Not sure how close you're wanting to be to the park, but Mt Wam over in the Ten Lakes Basin area is rentable.
http://www.fs.fed.us/r1/kootenai/recrea ... twam.shtml
I've never been to the lookout itself, but I've driven over the road from Ten Lakes to Polebridge. I've been to Stahl Peak lookout which is in the same general area, I thought it was also a rental but I don't see it on the Kootenai NF list. Weasel Cabin is an old border patrol cabin that might be a rental, again its in the Ten Lakes Basin area, but its near Weasel lake so the access would be easier but the views not so much. Wolverine Cabin is another border patrol cabin, that the Forest Service rebuilt a few years ago, I think its about a 3 mile hike into the cabin, I've stayed there, I don't think its a rental, just first come first served.
From Polebridge, you;d need to go north and take the Trail Creek road west, past Tuchuck campground to get over to the Ten Lakes Basin area., or go north from Fortine on the Graves Creek road.
I have friends and relatives who have stayed at some lookouts in the Yaak, (north of Libby, west of Eureka), but thats getting quite a distance from Glacier, Webb Mtn Lookout is where they've stayed.
http://www.fs.fed.us/r1/kootenai/recrea ... uide.shtml