They can be found in at most major car swap meets. Saw a bunch at the Turkey Run swap meet in November. Also usually can be found at swap meets at large Good Guy events. Also available refurbished for a hefty sum usually in the $400 ea price range. Not all Rochester 2G's are setup for use in for tri-power, but peedway has a nice kit for coverting the standard 2 g's into a tri carb setup. The c in 2gc stands for center, as it is specifically setup for use as the tri-power center carb with the proper shaft and features.

I have three really nice ones mounted on a offenhauser intake on my 57 Olds but I really don't thing you can afford them.