Rick Kuehl used to make 20" A2 .22LR uppers with stainless barrels and regular HGs (no FF tube), but has ceased production. I got his second to last barrel but I don't know if he sold the last one or not. Wouldn't hurt to call him and ask I guess.
A while back people here were saying Fulton Armory was selling barrels like Rick's. IIRC they weren't on the web site so you had to call. If you can find it the thread that mentioned them was about Kuehl.
Kurt at
KKF lists a 20" A2 HBAR upper on his .22LR page, and he could cut it down to 16" for you.
By the time you factor in the Ciener to go with one of the above barrels you could probably just get the DPMS A2 with the FF tube. It could be cut down just like any other barrel, and if the 'smith has to take the FSB off to do the cut-down he could put a regular barrel nut and HG cap on for you and you could sell the FF tube.