I have been building a film processor for my darkroom to allow better temperature control than what my Unicolor motor base can provide. Taking a note from Jobo, I use their drums, but everything else is off-the-shelf parts from the hardware store or kitchen supply store.
The base is a 36x18 inch piece of melamine intended to be a bookshelf. I reinforced it with perforated angle steel and bolts to prevent sagging, then installed leveling feet. The water tank is a stainless steel buffet tray from the kitchen store with a perforated tray to provide a raised surface above the heating element.
The heater and pump are from a pet store and hold the water steady at 100°F very well. The thermostat on the heater only goes to 92°, but it had a slot in the back for an allen wrench to adjust it, so while it reads 92° on the dial, the actual temperature is 100°F. The pump is a small submersible one for lizard tanks.
The drum is supported by two stainless steel rods that rest in some of the perforations of the inner tray. The rollers are teflon rod that came with centered holes, I just cut them to length. I am still building the motor section, but it is the guts of a Unicolor base put into a new box, and I have removed one of the large wheels from the axle, then extended the axle and placed a large fender washer on the end to connect to the magnet on the base of the drum. I'll post pictures of that part once I finish it.
I built this for the challenge, and for the fact that I can easily replace any part without having to hunt down old Jobo parts. My motor may eventually give out, but I'll cross that bridge when I get there.