tires in Mendoza Argentina or Santiago Chile or near

[road spirit]

Hello

In September I will start a road trip across S.America. My girlfriend will be riding with me on my F800gs.

We will start from Buenos Aires, head north to Iguazu then cross Paraguay, enter again Argentina heading to the Chilean border. From there we will ride Bolivia, then Peru through the cordileras all the way to Ecuador.
After reaching the "center of the world" we will turn south and cross again Peru, this time on the pacific side. Continuing south we will ride Chile and Argentina until reaching the end of the route at Ushuaia.
Finally, we reach again Buenos Aires and return back to EUrope.

According to that plan, when we will be near Mendoza our tires (heidenau k60 Scout) will probably need a change.

Now, from my research I see that tires are too expensive in S. America (almost double or triple the price of that in Europe) and also it's hard to find the suitable type (for example TKC80 or Heidenaus K60 etc)...

Am I searching wrong? Could I find similar tires near that region at a reasonable price?

Otherwise, ideally I would like to bring with me one extra pair of tires but since we will be 2-up on the F800gs and with all the necessary luggage for 2 persons and 3 months it will be really hard to carry the tires all the time.
It would be nice if I could find someone in Buenos Aires to keep the extra tires for me, then when the time comes I would contact him and have him send the tires for me to an adress that I will specify (probably in Mendoza). Of course all expenses will be paid by me in advance.

I know that this is probably too much to ask from someone with whom we've never met before, but I think I should give it a try.

Saludos
John