How can I fix my wall light micro pull switch?

The pull cord on my BHS wall light unit has stopped working - it does not recover its on/off position. Fortunately, it failed in the "on" position so I can now only switch the unit off/on by using the fused unit switch on the circuit.
Could I purchase a replacement Micro switch for such units and is it possible to repair? This is one of a pair - the other works fine so do not want to have to buy two new units - assuming they are still available.
No name or model number observable within the brass enclosure case:they about four years old.