I don't know which kind of chair you can find in the US but here's the best chair I found in Canada:
http://www.bouty.com/en/node/440
You can really customize every part like the armrests, mechanisms, base...
For example, most chair I found could only adjust the height of the armrests and the surface wasn't straight. Here, you can make a ton of adjustments:)
Slashdot Mirror
I don't know which kind of chair you can find in the US but here's the best chair I found in Canada: http://www.bouty.com/en/node/440 You can really customize every part like the armrests, mechanisms, base... For example, most chair I found could only adjust the height of the armrests and the surface wasn't straight. Here, you can make a ton of adjustments :)