I seem to remember a post on here with a link to a "switch valve" (or whatever it's called) that lets you automatically rollover between one propane tank to another. $38 rings a bell. Is this right, or am I thinking of something else?
Yeah, any RV place should be able to fulfill your needs. But at that price I think you are talking a manual switch.
I use propane for my cooking in the cabin and the least expensive auto switching regulator I could find was about $90. THere were manual switch regulators in the price range you suggest but not the automatic type.
Any propane dealer or RV place should be able to help you, but I would price the propane dealer first.