If you have not already found a chair try this website. I have one for my long arm but can't remember where I got it. I have the Arrow chair for my Bernina in a table. Absolutely the best sewing chair. Perfect height and I have tried many chairs.
www.sewingmachinesplus.com/sewing-chairs.php

there are a few threads on the apqs forum.......

Any suggestions as to where to get a chair to use with my longarm machine?