I'd suggest talking to veterinarians. As you can imagine, it's often necessary to euthanize patients, but it's not necessarily in the scope of a veterinarian's care to help you with the rest.

If a vet could say, "Visit _____.com, which will help you find services for memorializing your pet," it would take a lot of pressure off of them. They already do that for services that help plan home-cooked meals, insurance, etc.