Originally Posted by thatfreaknguy
but ive also been told another markers cup seal will work too
The older pre-99 cockers and snipers used a similar cupseal. Its slightly shorter, but does work. Lots of aftermarket companies would sell the same cupseal for both guns.
But like capitalpaintball said, smoothing out the valve seat, and adding some good lubricate can usually fix 75% of the leaks.
EDIT: Also Palmers sells new replacement tune-up kits that includes a new cupseal. PTP sells them also, but I believe have sold out of New/Old stock. Ron-ASP on ebay always seems to have them for sale.