Sottini ceramic disc valve

[craigskelly]

I have a Sottini bath/shower mixer which uses a 1/4 ceramic disc valve. The retaining clip is broken allowing the spindle to rotate fully (not just 1/4 turn).
Does anyone know if it is possible to buy a new retaining clip or do I need to buy a new valve assembly (have been told Ideal Standard are compatible)

 

[WHPES]

Normally replace the cartridge as a complete unit.