http://jobs.arduinoexperts.com/
I have no experience with that site so this is not an endorsement but merely a helpful hand to hopefully expedite your search.
You may be able to find someone through a more direct route (user groups; vendors; Google)...
http://maps.google.com/maps/ms?ie=UTF&msa=0&msid=106367500863692290311.00048bf511125d88d5fc7
http://www.arduino.cc/cgi-bin/yabb2/YaBB.pl?num=1272714602