So far I'm diggin' the Culturelle. $15 for a 30-day supply and you take it once a day. It has a massive blend of helpful pros, Lactobacillus and Bifidobacterium among others. I got it from the "natural" grocery store. Does not need refrigeration. So far, so good.
I also started taking calcium polycarbophil (FiberCon), which can help your intestine resorb water and cut down on the diarrhea you suffer from. Despite having 3-4 episodes of diarrhea today, I also had a solid stool for the first time in months! It was a glorious moment!