I know you want more than one strain of bacteria in a probiotic (at least Bifidus and Acidophilus).
If going with one from the vet, I would go with Proviable over FortiFlora. However, this is one of the most recommended on this site:
https://www.amazon.com/gp/product/B0041U6OOG/?tag=&tag=thecatsite
If going with one from the vet, I would go with Proviable over FortiFlora. However, this is one of the most recommended on this site:
https://www.amazon.com/gp/product/B0041U6OOG/?tag=&tag=thecatsite