I'm not sure if a stock ambi-safety will be compatible as I think the 15-22 is a bit wider than a standard AR. I was able to put in an aftermarket safety into mine. It works just fine but it is recessed a bit on the "non-lever" side. So that could potentially cause problems with an ambi safety. However, if you find one that works please let me know as I'd like to put one on mine.
Otherwise you can always make your own which is what I was considering doing if I can't eventually find one that will work. I remember seeing at least one of the other members had done so already.