Option 1: The Vet. Probably the most costly, but it’s good to get your pet in for a checkup.
Option 2: Mobile clinics. They move around and are reasonably priced
Option 3: Non mobile clinic: Vetco on Sundays at Petco
Option 4: Humane Society or ASPCA if they run shot clinics
Option 5: Spay Neuter clinics offer discounted rates for shots along with their many discounted services

For our four cats we went with number 5 this year and took every cat in their Wacky Paws carrier in the back of my car. Each kitty took it like a champ, but Stewart got sick for the next 36 hours or so. He wasn’t eating, vomited once as soon as we got home, went into hiding, refused wet food, screamed when we’d touch his butt. The benefits of vaccines outweigh the risks. Maybe he’ll do better this next time around when we go for shots again. I have never had that happen with a cat that I’ve vaccinated and we’re looking at it as an isolated incident. We’ve gotten larger problems with that cat now… spraying. Eesh.