We stayed at Silver Creek West when we were unable to get a campsite at Craters of the Moon.  Silver Creek is a disperse camping area as no established sites are in the area, but their are several rock fire rings in the area.  The site does have a vault toiler.  Camping is free.  Plenty of flat ground for your tent.  We were visited by a moose as we packed up camp in the morning.  No water or trash service so come prepared.