We found a set of campsites specifically on the forest road 705F, near the Hidden Valley picnic area. The sites are free, as they are primitive set-up with only a fire pit. Although there are not facilities immediately there, if you finding camping in this area you are close by to a bathroom at Summit Trailhead and potable water at either Hidden Valley or the Abraham Lincoln rest area. We found a whole list of forest roads that allow dispersed camping 100 feet off-road: https://www.fs.usda.gov/Internet/FSE_DOCUMENTS/stelprd3841999.pdf