I have no idea if something like this would work, but there seems to be a lot of interest in an armrest. Check out this link to a German manufacturer of Audi TT aftermarket parts. This seems like it might work, but the base might be too short. Also is a link to to a USA distributor. Unfortunately these are bank and may be prohibitive to trial by error. Anyways, maybe work.

German manufactur
[/url]http://www.tt-designparts.de/products/det_arm.php

USA Retailer
http://www.stratmosphere.com/tt_armrest.htm

 

http://www.tt-designparts.de/products/det_arm.php

http://www.stratmosphere.com/tt_armrest.htm

 

pretty smooth and kind of fits with the circular air vents etc. hmm..