Pyrodex RS or P will do just fine. I actually like to use either a knight red hot #11 nipple or a stainless steel spitfire hollow base nipple.

If you CAN find goex or the real stuff locally, i'd suggest you get a can of 4f and while hunting, pull out your nipple, and just do a fine sprinkle of 4f right on top of the Pyrodex. Just gives it a little boost in cold weather. A little extra insurace is always good.