I would look at Civil War sutlers first. Fall Creek Sutlery, Blockade Runner, S& S Sutlers, C & D Jarnagin and Regimental Quartermaster. You may not be able to find the exact material but thin striped were common then.
If you or a friend are handy with a sewing machine, go to a fabric store and buy striped 'osnaburg', 'canvas' or 'ticking' material. You can buy piercing buckles from a Civil war sutler and make them. Needle & Thread in Gettysburg has material and the period hardware. Not as quick as using a card and ordering a pair, but you'll be the only guy who has em'!
Good luck,
PhP