Second Bigkahuna's suggestion you contact Bydand Forever, the California-based reenactment group:

http://www.bydandforever.com/an_introduction

Note that this group is officially sanctioned by the regimental association, and has "hopped the pond" to participate in events in the Gordon's "home country". Like any good living history organization, I would bet they have fairly detailed uniform guidelines and recommended suppliers for their impression.

T.