Try the Revolutionary War mailing list, here, where you can register and look at messages:http://groups.yahoo.com/group/Revlist/
The list-members are mostly re-enactors. The group re-enacting the German Regiment may have their own website.
Use the search box, maybe you'll find really helpful items.
There are also a huge number of photos, maybe just what you are looking for. Bear in mind that artists, book publishers and photographers have copyright ownership of their work, and it cannot be used without their permission.