OO! Here's what Debi suggested to me for my musty Saddlery bag:
Brush the inside seams with bleach. Dunk, reshape, dry.
Get Leather Rejuvenator and apply according to the instructions (I found it listed as "Leatherique Rejuvenator" on Amazon.)
Wrap it in a plastic bag to allow the bag to absorb all the rejuvenator. (This helps with the dryness of the leather.)
Then apply Leather Therapy Restorer and Conditioner to help inhibit mold and mildew.
Unfortunately I haven't done this yet so I can't speak to how well it works, but I totally trust Debi's recommendation. The rejuvenator arrived today so I'm probably going to apply it soon. And the other downfall is the products are not cheap, but hopefully last awhile since I'm not planning on dealing with musty, moldy bags any more than I have to.
Thanks! Will give it a try. I have a stinky old watermelon bag to deodorize too. Mo money, mo money....