Fortunately, after several weeks of asking around, our main construction guy, Nilton, got a line on one out on the islands that had been stripped and was sitting unused. He made a deal with the owner of the shell, and for $190 we had ourselves a pretty decent sized mixer that needed some TLC, brought in on a canoe from the islands!
There's a good amount of rust on it, and it's missing the pulleys and motor needed to drive it, but fortunately all of the important parts like the mixing drum, gears, and bearings, seem to be in pretty decent shape!
After sanding it all down, the workers hit it with a coat of primer and some good enamel, and now it's looking pretty good!
The last big piece of the puzzle was to find the proper pulleys to reduce the speed of the generator motor we have to make work with the mixer. After searching around in the used parts market here (which is mostly parts taken off of cars) we realized that finding a pair of pulleys with the correct diameter to gear up the motor to be able to spin the mixer drum and with the correct shaft diameter was like looking for a pair of matching needles in a haystack. I thought about heading down to the local Grainger or McMaster-Carr to pick them up, but... alas, there are none. :) We didn't have time to wait for the mail, and UPS could've gotten the $50 parts here for about $400, which also didn't seem like a good option.
Fortunately, we heard about a short term team coming over, and they very graciously agreed to surrender 20 lbs of their luggage allowance to bring the parts over this week! We'll be ready to hit cement production hard next week, so hopefully we'll get the parts and get the mixer fixed before we even miss it!