There was only ever one handle fitted to the rear doors on the near side so both doors open at the same time. I fitted a small bracket to the other door that a member on here have me, it's off a vending machine but it would be a simple job to make one out of a bent piece of flat bar.
It has a square hole that just happens to match the drive on the lock spindle and I pushed a piece of rubber hose over the end for a confy grip
I put a handle from a lever ball valve. The wooden bit is the lock. It has a slot in it that the handle slides into so it can’t be opened from the outside. I can’t add the photo because the reception is terrible