Right now I'm closer to Burien, WA than Guatemala City, I'm going to be in Cranbrook, B.C. for the fall. Normally I'd be about 20 minutes from the airport in Guatemala. If you're going to be in Costa Rica check out some wreckers there. They go by the name "yonker" in some areas of Central America. When going to wreckers in Central America is usually is helpful to have a sample of what you're looking for.
If you have a longer layover in Guatemala, and are brave, Zone 8 in the city is a great place to find automotive parts. Take a trustworthy taxi there and cash as well as a sample of what you want and there will be guys there ready to help! Tell the cabbie you're looking for car parts and want to go to Zone 8, he'll know where you mean! It's the strangests kind of a place, and NOT safe after dark.
Guatemala is not the best bet for HJ60 parts though as there are more FJ60's there. Honduras is better for HJ60's and that's where my contacts are. There are two wreckers outside of Tegucigalpa, Honduras, one about 20-25kM towards the coast and another about the same distance the other way. Both always have several HJ60's on the lot.
Again, if it's Guatemala or Costa Rica, I'd bet on Costa Rica for finding those parts. Maybe they have a place like Guatemala's Zone 8 in San Jose. It's worth the asking.