Having visited many times, Colter Bay RV and Colter Bay CG (the dry camping part), Grizzly RV, and Baker's Hole, are all great options. As far as Bakers Hole, it is our favorite - great spot even for big rigs. We've been fortunate enough to snag a spot driving straight in twice, another not. So, what we did, was stay over at Grizzly RV and early the next morning, we drove over to Baker's Hole, spoke to the hosts as far as which sites were coming open and then drove through and if a site didn't renew, we put our pay envelope on the site and paid for it, then after it cleared, we went back to Grizzly, hooked up and drove over to Baker's Hole. Any FS CG with first come first serve sites, we always stop and talk to the hosts first. It's the best lesson we've learned in getting a spot. Another spot we've stayed at is Red Rock RV - out by Henry's Lake. Super nice RV park. We've also stayed at the KOA West of West Yellowstone. A nice place, but spendier than Red Rock. Another couple of years, we stayed even further out off of the Togwotee Pass between Moose and Dubois, Wyoming at a FS CG called Falls. Two loops with lots of spacious sites for big rigs and one loop has electricity. Staying at either Henry's Lake, Red Rock, or at Falls means that you'll have a drive in, but if you don't mind, these campgrounds are worth it.
