When I traveled with my spaniel who had CHF, I looked up in the campground phone book Pet Crematory services... found that some funeral homes do this service. My last trip out with Bailey, thought for sure this was going to happen. I did have an emergency vet appt and he said he would come in if needed. Also, there was an all-night Emergency Vet service in town who, when contacted said they would help out. Also, have asked campground owners/employees who they recommended for vets in their local area.
I would have opted for cremation and waited on the ashes, but fortunately Bailey made it back to home area and lived another 6 weeks.