This is a late response and I don't know if its doing anyone any good but for the record I am glad to hear I'm not the only person whose had the crazy idea of adapting a Cambo reflex viewer to a Toyo view camera (in my case a CX). I found mine on ebay for $125 at 5:00 on a Sunday morning with the Buy It Now option. There wasn't time to find out whether it would work or not, but after concluding that there was no way it would lock onto the Toyo, but could probably be easily held to the ground glass manually (by hand), I went ahead and bought it. Then on the way to work I had the worst thought: what if the Cambo viewer was too wide to fit directly on the ground glass?

It's twenty four hour later now, and I've had a chance to call up Calumet, and the guy confirmed that no it wouldn't lock onto the Toyo, but no it's not too wide and should be able to be adapted. Whew!

In any case I am still waiting for it to delivered (obviously), so I can't tell anyone how well this setup works yet, but at least according to Calumet it is possible.