Does anyone know what the make-up of this system is?

The reason I ask is, my Williams 1 did not come with an IR plip key (the former owner lost it 10 years ago!). The car does not have an immobilizer, so it would literally only be operating the central locking.

Is there a 'control' box I can source from a breaking car that still has a working IR key; then replace mine with that one?

Any thoughts?