I sold my M4 sometime ago and have since gone with an M1 tricked out but I'm getting the M4 bug again. I still have the pistol grip stock in the box from when I switched out the stock to a standard stock.
If you order via brownells you can them and ask for their special orders section to order the stock, it might show up a little faster, that is how I did my last M4 Benelli stock.