Having been through my boxes of parts for the Midas I have come across an expansion tank which came from (according to the part number) a Mk2 Ford Fiesta.
I have no need for it, so it's a freebie, and might be useful for a project. It's missing one of its mounting lugs (easily amended with some clever use of today's epoxies and some bracketry). It will also need a clean inside, so you'll need to get the pasta out. Comes with a cap!
You can either pick it up from Central Ipswich or I can post it 2nd class recorded to UK only for £4.