In reply to Rockatt:
Type Prana Bronson Pants and your waist x leg size into eBay search bar and you should see a lot available from the USA. Postage seems to be standard 25-30 quid and prices all around the same 25 quid, with 'make offer' for some, so you might get a newish pair for about the same as they were in the sales in the UK? Shouldn't be any customs duty?
Bear in mind the cut of the trousers changed slightly over the years: some feeling slightly looser in the thigh and waist as they go from 'made in China' to 'made in Sri Lanka' and adding the writing 'Born from the Experience' on the inside waistband. So you might want to match the iteration that you have as close as you can to the photos of the used pair.