Champion brass antisyphon valves were so common in California that their use is seen in neighboring states, and hardware stores would have repair parts. Try an Oshman's near you. Heck, try any hardware store near you. Champion has a few applicable repair kits, depending on whether you have an antisyphon valve, or just a vacuum breaker. Try RK-31-C as one part number. Also, Orbit has a knockoff of the Champion antisyphon valve, and they have a parts kit for it, with the number 53066. You can't swing a dead cat on the internet without hitting a vendor for Champion (and imitators) parts.