Aye Simon,
Whilst Nigel Lacey has transferred the spares side of his business to Doug at "Mdina Italia", he still retains a large volume of secondhand spares, mainly engine components, but definitely worth asking if he has, or knows of the whereabouts of a smooth top yoke for an Elite 200.
Probably best to contact him, with full details, including dimensions, using an email to this address and await his reply:
info@laceyengineering.co.uk.
I hope this helps. Better that yours snapped in the workshop rather than when being ridden.
Good health, BillR