Thanks everyone for offers and suggestions.
No luck finding anything yet. Piher do a close one but it will require some shaft adaptation and the hole is slightly too small. Original was a Citec unit.
So after much wiggling and swearing, a Citec 2.2M linear carbon 20%, 0.25W, 250V max rating. 8/10mm hole, 4mm shaft pot popped out.
There's a close-ish Piher one available on rapid but shaft is 6mm which will require some mechanical adaptation but should do the job. Will try TME and some other shops first and the junk box as I've got hundreds of the damn things in already.