We found dry ice in Riverton to get the two opening day antelope in our group froze down. Several days later when we headed home with 4 goats everyone was out as we headed from Shoshoni to Riverton and on down the road. We just used block ice until we got home after finding that. I'd probably get a cooler full of dry ice in Casper or somewhere on the way and keep it in the hotel unless you are camping. Then move it to other coolers as needed.
One of the guys I went with has a real small freezer that would fit 4 goats just about right. We came up with the plan to throw it on the back of the truck and put it in the hotel room next trip on one of those big Husky liners he has for the back of his Suburban to make sure the carpet stays dry. Once we get everything froze down and head home 4 of us should be able to set it back on the truck, find dry ice, and get there. We could make our own block ice for the cooler we haul along during the day, and for the trip home too.