Don't forget the interchangeability with the Morris Minor. There are a lot more Minors (and Minor Spares) out there than MGs and, strangely, Morris spares are cheaper!.
I turned down an original cap last night when collecting some J engine parts. Drop me a line direct if you are still interested and I will put you in touch direct with the chap who still has it
What an awful cap! I have a nice original I'll look it out today and get a photo for you. It's a nice cap with writing on it. It will be £30 plus postage I'll get some photos later.