Doesn't that defeat the purpose of using the found items in the first place though? If you're going to put all that effort into modifying an unsuitable item to pass CRLs (which it's not a given that you'll ever be able to make it work, btw, they're pretty good at spotting banned items) then you might as well put the effort into doing it right from the start.
On the other hand, if you're looking to buy pouches, Liberty Tree Collectors has a great vintage WWII pouch selection. Prices start around $8 for a double pouch, and their stock usually cleans up nice. It's where I got all of my pouches from.