I was looking for ergo chairs yrs ago and found the Swopper, have you seen it?
http://www.sitincomfort.com/swopper.html
I liked it but 500+ dollars was to spendy for me.

I found a luxurious executive LazyBoy Office chair at a thrift store of all places 30.00 and it was mine
I also have a Panasonic shiatsu massage recliner. {a high end resale store purchase}