Since I'm still waiting on a lot of other parts to come in (more than likely for a future run!), I was finally able to track down some canvas that looks to be exactly the same color as used on the bowcaster. The canvas is slightly olive green with a bit of a tan hue to it. I then dyed it a little darker brown to fully get it to the correct color. I did have to cut it to the correct size which is surprisingly thinner than you'd think.
I put it next to the o rings I'm using which are the correct size, and I also pictured it with the accurate strap to show the color differences.


I put it next to the o rings I'm using which are the correct size, and I also pictured it with the accurate strap to show the color differences.

