The reason the Ricoh camera is listed as 'unsupported' on the Supported Cameras list, is that for some reason, the company decided to use an extremely non-standard remote trigger, known as the Ricoh CA-1. For one thing, the CA-1 needs batteries to operate (!), and it's an USB plug, but it uses specific signals to take a photo, rather than the simpler 'close a connection to take a photo' approach. Of course, the fact that a remote control exists means that you can use the Triggertrap, you just have to do a bit of hacking...
The first and easiest way would be to buy a CA-1, open it up, and add an additional wire to each side to the trigger connection inside the remote control. Wire those wires to a female 3.5mm mini jack plug. Then, simply run a cable from this plug to the Triggertrap V1 or Shield for Arduino, and you're home free.
Alternatively, you can build a CA-1 yourself using these instructions. Instead (or in addition to) a switch, add in a 3.5mm mini jack, and you can talk to the Triggertrap.
Finally, It may very well be possible that building the Triggertrap V1 to CHDK bridge would work on Ricoh cameras as well, but this is yet untested. If any of the Ricoh crowd could report back, that'd be spiffing.
I'll be honest; I don't think I've ever met anyone who uses a Ricoh camera; but if any of you do, then please do report back with your findings!