Hit the local musical instrument store, and look at cheap drum thrones. They sit about chair height, and are as close to a low stool as you can get. Darn comfy too.
You also could hit the local OfficeWhatever store and get an armless office chair, and just not put the back on it. I've seen $20 or less brand new assemble-it-yourself office chairs.
I use the chairs out from under the kitchen table...