So, turns out the UK company that said they could make faux leather ammo pouches, can't (sounds like they tried, but it just didn't work out).
I've contacted Geeky Pinks for a quote as they've also said they could make them, but there's then the additional cost of international postage.
I can get canvas pouches for £40 each, and was thinking of painting them in matte PlastDip, then weathering to give a leather appearance. Anyone tried anything like that before, as no idea if it'll actually work(?)