Where can you get your rabbit neutered when the vet doesn't do rabbits?

Yes, a rabbit-savvy veterinarian can do it. It is recommended to do it as early as possible, as it has lots of benefits : a neutered/spayed rabbit will stop marking it's territory, will have less aggressive behaviors and destructive habits (chewing everything, etc) and it will extend it's lifespan, among other things.

Rabbits will still mark their territory even if they have been neutered. It is something all rabbit do, a wild rabbit trait. They just might not do it by spraying, they will still urinate and defecate to let other rabbits know they are there and they are patroling their area. Neutering a rabbit will not curb it's chewing behavior.