From everything I have seen, the Magpul BAD lever will not fit the 15-22. I do know there are a couple of companies that make something similar though; NDZ performance is one.
Figured I'd pick one up for my new rifle, and pass along the gouge to the rest of the crew.
44MAG.com - Smith & Wesson - S&W .22lr 10rd Short M&P15-22 Magazine Smith and Wesson