.Red Rock Canyon in Idaho(about 15-17 miles to the West Entrance to YSNP). Great Campground off the beaten path near Henry's Lake. I just got an E-mail from them indicating a change in ownership and many upgrades they've done. Might be worth a look.
We stayed there years ago and had a great time and the drive wasn't all that bad!
We also had a very good experience here at Red Rock. It is in a lovely area--Island Park.
Henry's Lake State Park is nice too with most site having water and electricity and a few with sewer too. Spacious between sites and a view of the lake from every site
We stayed at Henry's Lake State Park more recently than Red Rock and also had a great experience. I can heartily recommend either of these two parks in this same area.