I went looking for all the threads on here a while ago asking about putting an A2 style stock on the 15-22 and everyone saying it can't be done, but I could not find them.
Things are about to get easier.
Magpul fixed stock for carbine length buffer tubes. Not released yet, and not an A2 style, but it is getting there.
I do not know if the ATF will still regard it as an adjustable stock, something they do with some other "fixed" stocks, but it may be an option.
This one is designed to be used on a standard AR-15 with a castle nut, which the 15-22 lacks, so some creative construction may still be needed.
KBK