If you don't mind dealing with re-enactors (apparently there are some people who do) and you are based in the UK (or thereabouts) try contacting a group called "Britannia" (I don't know if they have a web presence, but they probably do), they speciallise in late Roman/Romano-Brittish so they may be able to help, failing that "Regia Angolorum" (www.regia.org), they are a little later (9th - 11th Century IIRC), but they may be able to help.

Walrus