I would just make them out of canvas. You really shouldn't be showing them off in public anyway, as they were worn under waistcoats, so who really cares what they are made of? If you think you must have something like this, and they might be seen in a camp, you could opt for the single gallus, of linen or canvas. (It just "offends the eye" less..., no documentation either way.)
How far does it go back? Tough to say..., how does one document what would not appear in artwork, nor be seen by observers? Example..., How far does the corn cob pipe go back? Herringbone weave for wool was known in the 17th century, but seems to have disappeared in the 18th century, only to return in the 19th century. Wierd. So..., do what you need to do and if anybody asks, tell them you don't have documentation prior to the French Rev or so, but you need 'em. (I like braces as it keeps the sciatica away; I wear them under a waistcoat so what's the harm?)
LD