Gannaway Leather Primer
Gannaway recommends priming a new bag and re-priming "once a year to maintain maximum tightness" of the pipe bag. The bottle equates to one application. This is a latex product that helps to seal the bag.
 
Note:  If you have a zippered bag, cleanup will be easier if you lubricate it before applying the primer. Try not to get primer in the zipper teeth.