Well, if you were heading this far south I have a few references. I started out by calling veterinarians around town when I began looking for a snake avoidance class.
I have used Horizon Veterinary services in Lewistown, MT and they are a great veterinarian clinic. You might give them a call and see what they have to say.
Another option is to check with local dog training clubs as that is where I first had Drake snake proofed and his was done at a pointy dog club (my Quail Forever chapter just put on a clinic this year where I took Belle for a refresher since the first class...put on by a local herpetologist... didn't seem to take with her).
Have you considered giving Beaver the snake vaccine? For the first series it is a two shot vaccine, two weeks apart I believe. After that it a one shot annual booster. It won't immunize the dog from snake venom but according to many vets out west, it often gives dogs extra time to get to the vet (out west that is good) and often the dogs need fewer antivenom vials (very expensive). There is a lot of controversy surrounding the effectiveness of the shot, so do some reading (if you haven't already done so). My vet doesn't give it here in FL (it is more for western diamondback venom) but I can get it from the vet clinics that are put on by Tractor Supply. I just have to call ahead of time and request the shot. The way I look at it is that $25 for the shot is not wasted if it potentially gives me the extra time to get my dogs to the vet if they get bit. Luckily, I have not had to test it (came close with Belle in MT).