I'm afraid the news is not too good from this side either. I went to Evans and they have had the XLite salesman pass through with one of the stems you were looking for. Apparently it's quite a stubby shape, so the guys told me, but they've been told they wont have it in stock until mid-October thereabouts.
Pretty much the same for the disc brakes. They phoned the distribution outlet, and while they can get them on special request, they've also been told not until October again.
They could not confirm in either case what price they might sell for. They did say they probably could send overseas but they've never had anyone ask for that, so that would need a decision from 'upstairs'.
I've got to know the guys at the shop quite well and I can trust the information they gave me. They know all about Steve Peat and one of the guys in the shop whose into dh type things has said the stem looks good enough to want it buy it whether he needs it or not!
Sorry about the bad news.
If there's anything else you'd like me to pursue, I'll be happy to stay on the 'case'.