Scutch - I had the battery covers custom made - I sold about 30 of them when I was selling them
Can still get them if anyone wants one but prices of metals have gone up so they would work out about £40 each - top quality though and worth the money!
With regard to polishing OCD is a massive help - I've never found a metal polisher that is willing to do anything awkward so all corners etc come back untouched - this wasn't acceptable in my eyes so spent hours with a Dremel, polishing felts, various grades of wet and dry and loads of metal polish, between the writing is a complete pain in the arse but worth it in the end - was very proud of that bay!!
In case you haven't seen it here's my existing bay