Not sure about Central America, but 19" 110/90 can be found in South America. In Quito, Ecuador contact Ricardo Rocco at
aroundforpeace@yahoo.com or Albert at the Turtle's Head Bar (in Lonely Planet) for moto shops with tires. In Santiago, Chile, go to Lira Street. The first 5-6 blocks on the northern end of this road are full of motorcycle shops. You can find 110/90 19 tires with little problem. Peru, seems to be none available, but contact Jeff at the Norton Rat's Pub in Cusco. He tried to find one for me via contacts in Lima, but had no luck at the time, but may have better luck when you are there. In Argentina, go to DakarMotos in Buenos Aires. Javier has a few tires in stock and I am sure he can get a hold on others. All three of these guys can be found right here on HU. All are great guys and true Moto ambassadors.

For a 110/90 tire expect to pay a premium. twice if not triple what we pay here in the USA. Even though 19" tires are available, I ended up going for a 100/80 19" Pirelli MT60's because they are a lot cheaper and more easily found. If memory serves me, I paid approx. $60 in La Paz. My riding partner, paid big bucks for a Metzler tourance in Santiago, but they are good tires and he found it worth the extra dinero.

The big tip though is to contact the local HU communities (links on the left of this page) of the regions you will be traveling through. This is what I did and they were invaluable.

Don't worry about the tires to much. Just plan ahead while on the road.

Have fun!

Ryan

ps - if you need a tire when nearing Quito and want a specific tire contact Racing Parts(if memory serves me well they are located at the south end of the international airports runway) Ricardo or Albert should be able to get their contact info. They can order most tires for you, but they will need at least 3 weeks notice for delivery and most likely a credit card. Again, you will pay a premium for these.