CBD oils are OTC in Washington state, the local co-op (grocery/sundry/plant store) carries them -- Lazarus Naturals and Restorative Botanicals (4 Paws Pet blend) brands
second mfg is is Colorado; first grows in Oregon, processes in Washington
I'm not up to speed on which states have what laws about hemp versus marijuana, or have decriminalized marijuana -- as you might guess, Oregon and Colorado have
I got a handout quoting veterinarian Dr. Robert J. Silver, dosing appears to be called out by oil in drops, suggest you coordinate with your vet --- but IMO you may not have to order it through the vet