There's a bunch at Staples.

I also just found some plans, might make one so it's adjustable my way: http://www.craftsmanspace.com/free-projects/kneeling-chair-p...

I still have (and use) mine.

They look awkward to sit on, you actually have to try them to realise you naturally adopt an upright (not slumped) sitting position.

There are a couple sitting about in my office. One guy broke his foot climbing recently and is using one as a footrest at present.

You can still get them. I'm sitting in one right now.

I'm impulsive, I blame you for the future amazon purchase. Used to visit my dad's office as a young child and always loved his kneeling chair. Nostalgia here I come!