Gene,
I think the proper general term in Spanish would Equipos de Ordeño (Milking Equipment.)
That might help with online searches. While these guys sell new equipment, often a seller
of new equipment has used stuff they took in trade or they might know of someone who
They've been around for a long time (80+ years,) sell all over the country (especially to Dos
Pinos associates) and are out of Quesada, Alajuela, which is about halfway between
Arenal and Alajuela city -- maybe not too bad of a drive for you for a day trip visit? If nothing
else that might give you a good idea about what all is available and what you might find on
the used market with persistence.
Equipos de Ordeño Siglo XXI
Av. 17, Provincia de Alajuela, Cd Quesada, 4400
400 metros Este de la catedral, Ciudad Quesada, San Carlos
Here's a nice route from Bagaces around the lake to their place:
If you do visit them, take lots of pictures! Who doesn't like shiny equipment pics? ;-)
Good luck,
Sam