Triton shower as1000 flow control valve no longer available?

Like another questioner, my triton as1000 shower won't turn off. I tracked it down to the flow control valve part number 82100160. This part is no longer available. Does anyone know where to get this part now or is there a way to fix it. I have contacted triton and looked at the sites for shower doctor etc. All list the part as obsolete and unavailable (doesn't anyone keep stock any more?). I have taken the part apart and it doesn't seem too complex, however, there seems to be something which is broken. Has anyone else taken a working one apart or have the schematics?