For the compulsory vehicle liability insurance for MEXICO you should be aware of the option of getting "Drivers license dedicated " insurance , referred to as DL from here on.
The coverage amounts in DL insurance will be the same as if you were to buy the " vehicle dedicated " trip insurance which you are probably speaking of when you mention buying another eight weeks of insurance . Both types will include provision for legal assistance and bail bond , some form of roadside assistance. Read the fine prints .
Take note however : the cost of the DL insurance will be much lower than buying the vehicle dedicated daily rated trip insurance.
After I discovered DL insurance have been buying that type of insurance for years with no complaints . **
Typically the trip insurance will be made out to you with the VIN , make and model of the bike ( or car) and the price will start at rate of , say $20 per day , for one day or for X number of days . For a longer period the daily price may be reduced slightly in steps up to a particular length of stay in Mexico . For a month you may be paying $300 or more .

The DL insurance on the other hand is made out to you and YOUR DRIVERS LICENSE NUMBER, with no mention of any vehicle name or VIN .
The beauty of DL insurance is twofold : the price is much less than vehicle trip insurance AND I am permitted to take different vehicles into Mexico on different trips under that single DL policy . (I know this versatility is of no use to Young1, but in that ONE year I am able to take several trips into Mexico with different bikes and the car , one vehicle at a time . )
In my case I discovered that I can buy a whole year of DL insurance for less money than I would have to pay for two or three weeks of the vehicle dedicated liability insurance .
If you are going into Mexico for a month you will likely be spending less for the liability insurance if you buy a DL policy . At most you would spend 180 days ,minus one , in Mexico which is the usual maximum length of stay on an FMM ( the Tourist Card ) . Again ,in my case I buy ONE ENTIRE year of DL insurance for $150USD, or I did until covid interrupted my travel habits .

The sources for this DL insurance are the same people who will sell you vehicle dedicated trip insurance but you need to ask them about it . In my case I deal with Mexusinsurance , out of Calexico , California . When I first visited their office in person , about 14 years ago they were the ones who explained the DL for me and since then I have simply renewed the policy annually , the most recent was for 2019 when a full year for that cost me $150 .
I understand that there are other insurance services which charge less still.
Whomever sells it , whether in Mexico or the USA , the insurance they sell is serviced by the very same Mexican-registered insurance companies , which may be subsidiaries of US or European insurance companies . Insurance for the USA is not valid in Mexico and vice versa .

** As for the type of full coverage vehicle insurance - fire, crash repair, theft - I go without on the premise that I will have to swallow that cost or loss ,because to me as a frequent traveller in Mexico the amounts of money required would soon be substantial . After 45 years and many trips in Mexico and not paying the premiums for full cover insurance I have saved enough money for the cost of a new replacement bike .
I think that this is what Grant referred to as being " self insured ". (?)
Your risk / loss tolerance may vary and you may want to insure to the hilt . But if you ride at a sensible conservative pace , keep you observation skills sharp and interact safely in traffic and watch where you park the bike your risk of loss can be dramatically limited . Avoid any and all contact between vehicles . Simply dropping the bike may cause some scratching and dings but full cover insurance may have a deductible so high that you will still pay for your repairs out of pocket .

As for Central America , the LIABILITY insurance is compulsory to have in Belize ,Nicaragua ,Costa Rica and Panama (2020) and it will be sold at each country's official border crossings , no way to not be aware of it . The cost will be very low . Each country's insurance supersedes any claimed general Central American insurance you may have bought .
The other Central American countries (GT, HN ,ES) do not actually demand that you have such liability insurance but it is wise to have it ,in case you do get into a small scrape with another vehicle , sometimes sneeky types do that intentionally in order to get some cash from you in a quick roadside settlement without getting police involved . Don't bite !
For CA insurance you may refer to the various insurance companies found on the internet sites and try buying it before hand , with reservation . The closer to the border you are you will have better ideas as to when and how long your stay may be in the next country and so you will better be able to buy the appropriate length of policy .
What may be the wiser and more practical approach for South America would be to buy insurance for such countries as you near the time when you will be entering them . Again some of them may have sellers of insurance at or near the border .

One of these insurers I can recommend for easy service is located in Guatemala and may be reached rather quickly by email and a policy can be arranged to cover Guatemala, as well as cover for Honduras and El Salvador. ( a friend did just that a week ago in Belize the day before he entered Guatemala )
This Guatemalteco Insurance company is called TodoRiesgo , with HQ in Guatemala City and agents in the various Departments of the country . For contact you may trcorreo - t - doriesgo.net and ask for Edgar Daniel Alvarado who deals with his district of the Peten . Company site is www.todoriesgo.net

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