Bag Straps for an older billingham

[filmtwit]

So I have an older billingham bag that I want to replace the strap on as it isn't really long enough. As it's an older bag it has the rust colored strap and ideally I'd like to find another one that's just longer. But alas, I can't find any rust colored straps online nor on the billingham website. Anyone have any idea where I could find a replacement? Hopefully a longer one too!?

Thanks,