Gohkann,
Great plains has a web site, they no longer seem to make the cooler BUT maybe if you contact them they could tell you who they
sold that product to, or if you ask for the oldest employee they have maybe you can get some good info.
By the way that's some really nice rebuilding work you did.
Evaporative coolers are just a fan blowing over a small waterfall. I am pretty sure after seeing your work so far you will be able to fashion something that will do the job.
Good luck to you, and let us know how it all works out.
P.S. We all love pictures.