Apologies for reviving this extremely old thread, but there was no update, and I figured it might be useful for anyone wanting to do this...
I picked up a cheap(ish) second hand pair of Remfrys, and the straps were pretty mouldy. Figured it wouldn't be much work to replace them, although finding the right material was hard - I couldn't find anyone that sold straps of the right width that were elasticated AND made of velcro loop. So I ended up getting it from here:
https://www.amazon.co.uk/dp/B01HBDVJNK?ref=ppx_yo2ov_dt_b_product_details&th=1After a mix up with sending me black rather than white, I got some 50 and 38 mm (sent out without extra charge!) that were a perfect match. Our sewing machine needles couldn't cope with going through so much stuff, so I sewed them on by hand. Not difficult, but ended up having to use pliers to pull the needle through (which also ended up bent).
An after photo. They really don't look that different or fit any better, but they do smell slightly better!