I bought one of those "bulk propane to stove" adapters directly from Coleman a year or two ago. I think it cost about $20. It appears to be a straight hose (no bulky regulator-looking thing anywhere in sight). One end fits a standard 20lb propane tank. The other end looks like the top of a normal small Coleman propane cylinder like you'd buy in a sporting goods store. The original piece from the Coleman stove that normally screws onto the sporting goods store cylinder (for lack of a better word) instead screws onto this bulk adapter hose, which in turn screws into your big 20lb propane tank. That original piece has the round flow control valve built into it, so you control your stove's hi/low setting just the same as always.

Remember, a few years back they changed the fittings on those 20lb tanks. The Coleman bulk adapter hose I bought fits the new style 20lb fittings, not the old style.

I'd just call Coleman and tell them what you have and what you want to do with it. I'm sure they'll sell you the correct adapter (they did for me). If you're questioning whether you've got a good setup now, I'd say just spring the $20 and buy what you need from Coleman. $20 isn't terribly much to spend for the extra peace of mind to not have to worry about "Should I have a regulator on this thing or not?"