IF you're willing to spend whatever it takes for a stay at Yellowstone, visit the website and get a room or two at the lodge. Plenty available via the online reservation system right now.
Figure on about $300/night, that includes a private bathroom with a hairdryer.
Every National Park I've visited, over 20 of them now, I've stayed in or near during the shoulder season, without reservations, and without drama. I have not stayed in Yellowstone, I don't really care to, it's not my kind of park. I've been there, seen the geyser, visited the prismatic ponds, got the t-shirt.
