Costco warehouse in Ocean, NJ carries 10 mg. They can order the 50 mg, price would be $47.08 for 15 tabs. Here in Mich, you don't have to be a member to use the pharmacy (just tell them at the door you're going to the pharmacy), and when I spoke to the pharmacist just now I told him I didn't think you were a member. You can have your vet call it in, they said they'd have to order it, need about 3 bus days lead time.
Costco
Ocean, NJ
732-481-0022 pharmacy number
I use costco for all my meds, their generic meds are very high-quality for humans...hth.