Looks like you could get away with shortening the strap and finding a friendly old biddy with a sewing machine. Likely a synthetic material which you can seal the raw ends with a match.
I think @Oldhippy has the answer. It may be quicker/easier to find a dressmakers/repair service which is able to do this for you. I had a strap for a backpack repaired ( they shortened it slightly by doubling up the damaged area) a while ago at the local place to me.