I know you have to do something about it, because otherwise you'll never feel happy at that place and with every declawed cat it would feel like a little piece of your heart and confidence are dying...
I think I've read in another post that you use "soft paws" on your furkids and maybe that could be the way to educate the people and the vet, because you are living proof how nicely this works!!!

I've often witnessed that people who are unsure already ask the staff at the vet's for their opinion and so you could just add "Happy cats have their claws or "Soft Paws"!"...
I think it wouldn't work for your vet to show him anything about the cruelty of declawing, because he sees this mess each day and he even makes money with it!!!

Best thing would be to achieve to ban "declawing" nationwide...it's already illegeal in most parts of the world!!!

I am sorry to not know any further suggestions, but I know a brave heart knowing to do the right thing is very powerful...be cautious (not to loose your job), but live according to what your heart tells you!!!

Wishing you all the best,
Sabine and Nellie