Wrist strap broke

My initial perception of it was that oh, they've changed it to a tighter one, how nice (I bought my first one 7 years ago). Then on the second day I was using it, the piece of metal holding the strap in came loose and not knowing what to look for, I couldn't find it. I just opened it and tried to use a piece of tin on my own but I couldn't figure out how to get it into the way it was. Now it just hangs all out, no way to tighten it. There is just so little space inside, I couldn't figure it out.

The design could be upgraded I think? It seems really fragile if it ever has to be opened. Should have been easy when they put money into designing an USB version I would think..