Yeah, I've spent a lot of time over in that area. Tropic Reservoir is just over the hill west of Bryce Canyon, but you get there by going south on a dirt road on highway 12, starting 3 miles west of the turn off to Bryce Canyon. There is a nice campground next to Tropic Reservoir called Kings Creek that is nice when you don't want to dry-camp. Powell Point is also definitely worth the drive and is really close to where you are.