[team-of-rivals]

I can't imagine that any ink pen/sharpie would adhere well to a wax pack. That is if it's in fact a 'wax' pack. My suggestion would be to lose the pack altogether and go with a simple blank index card. I've been in a bind myself in your situation and that has always seemed to work out for me. They work great for matting with a photo or simply as is. Either way, good luck and let us know how it goes.