I researched the same thing yesterday. Looking for something that promotes "active sitting". I came up with this list (for the German market). Most are quite pricey (in the 500-1000€ range):
○ Viasit F1 Move
○ Sedus Swing Up
○ Profim Accis Pro
○ Aeris 3Dee
○ Köhl Anteo Up with AirSeat
○ Rovo .. "Ergo Balance" models
YMMV. Bodies are different etc. I'm very interested in hearing about more options as I haven't ordered just yet.