ᐅ Reliable Traditional Roller Shutter Security

Hello dear forum,

Some time ago, we moved into a house from the 1980s. There is an old lift-up lock on (unfortunately only) one roller shutter. However, I cannot find this type anywhere, neither in hardware stores nor online. It is a standard plastic roller shutter with ventilation slots and a regular strap (but electric). I am not looking for the usual Schellenberg-style locks that are screwed into the wood at the top. Instead:

- a metal piece is screwed onto two slats
- the two metal pieces are connected by a kind of chain
- this "chain" runs inside the guide rail
- when lifting, it stretches and allows the shutter to be raised
- when pushed up, it dips and hooks into the guide rail
(>>> Nothing is screwed onto the door frame or inside the guide)

What is this type of lock called?
I would be very grateful for tips and links!

PS: Yes, I also believe this lock doesn’t provide high security, but the common lock is too thick for us, and my main goal is deterrence. Besides, I myself cannot lift this particular roller shutter up...

Regards
Peter