Actually, that strap at actiongear IS the 2 quart canteen strap that I mentioned in another thread... about this same subject.
It's what I've used on my PR and it works well, and is plenty long enough so you can sling the rifle over your shoulder while wearing armor.
The only thing better would be the thin nylon OD seatbelt webbing that was mentioned. You could probably cut the webbing off the canteen strap and use the seatbelt material to get an accurate reproduction, but you'd better have access to a machine that will sew material like that.
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