I bought a very nice little three legged seat from a store called "The Day Hiker". I think it cost me about $10+ tax.
I think this little folding seat is just about perfect for what you're probably needing one for. I use it inside my pop up blind, and it's really comfortable. It has three legs, and folds up kinda like a tri-pod. When you pull open the bottom of the three legs, it opens the little nylon seat, which sits kinda like a bicycle seat, but bigger. It sits very well on uneven ground which is a big plus when hunting.
I've used mine a good bit, and it's a rugged little chair, that as far as I can tell, is nearly indestructable from normal use. It also has a little shoulder strap that lets you carry it kinda like a sling on a rifle.
If you can find one, I think it'd be just what you'd need. Here's the number to the store in Pigeon Forge where I bought mine...
1-877-329-4453
Hope this helps.