We're located in Northern CA and after contacting EVERY talent search listed at Davidson, we found our solution through the Belin-Blank Center's talent search:
http://www.education.uiowa.edu/belinblank/TalentSearch/Default.aspx

They will allow you to do the test at your school, provided you can get a teacher, principal, etc., to serve as proctor. This way you avoid the long travel & related costs.

Our son will be doing it next month in a familiar environment, with his principal graciously agreeing to give the test during the school day. Total cost is $75 or so.

Win-win-win.

So get in touch with them -- I'm sure they can help you as well.

Ta-da!

Being offended is a natural consequence of leaving the house. - Fran Lebowitz