Just recently I met a guy from Las Vegas at one of my smoking lounges. I told him that I go there every June and he told me to meet him at a joint called En Fuego when I'm there next. According to him, they deal in some pipes (he's a cigar smoker), but their smoking lounge is apparently fantastic. Maybe give them a call to confirm whether or not they sell pipes.
It's slightly off the north end of the strip on Sahara. The same side of the street as that ridiculously large souvenir shop.
As I said, check to make sure they have pipes for sale, but if they do, definitely give that place a shot. This guy raved about it.