I tried an office chair, both a "steno chair" and a plain wood kitchen chair.
For me, they seem to be the wrong shape. The steno chair wants to cocoon me in the middle so I can't move sideways, and the kitchen chair doesn't allow me to get my feet into the right position.
Sigh.
Sooner or later I'll find something that works for me (and doesn't cost $6000). In the meantime I just take lots of breaks. π