You can try Cranimals, it's a cranberry supplement from Canada, a lot of my friends use it. It's a little bit expensive though. It also comes with a urine test for UTI for you to do at home.
I agree. I had a bulldog with chronic UTI's and cranberry supplements helped a lot. You do need to get antibiotics to clear any infection but the cranberry really does help with reoccurring episodes.
There are quite a few organic cranberry supplements, you should try them. Cranberry help prevent urinary tract diseases, it helps humans as well as animals.