Try looking at the local BMW shop they carry them here.
There might be some hidden away at the BMW shop, but if there are, I would guess they are old, old stock. I purchased an S1 from these guys http://www.extremesupply.com/index.htm
last October, and the mfg date on the tag was 2003. I tried buying one more in December, but their stock is greatly depleted--Schuberth stopped selling those models (R1, S1) in North America a while back. So, they're not DOT approved. As bad as this sounds, though, that will not stop me from buying another one. If they were approved at one point, then to me that means they're still safe enough to put on my head. Check out that link, CPG, but I would advise you give them a call--don't trust what the site says. They sell on eBay as well, and that's how I found out they were out of mostly everything they had. I bought one, and they sent me an email a couple of days later saying they didn't have my size... You bring up good points about parts, though. Don't know what's readily available. This link sells them, too. http://www.motowebshop.com/
(their stock is current--newest models avail.) I saw this on WT a while back. I emailed these guys about the VAT, and they said that for me (outside EU), subtract 19%, and that's what I'd have to pay (convert from Euros to $, so multiply web price (-19%) by about 1.58).
They make a great "flip" helmet. Is that a "flip"?
Negative, Buddy. That's all welded up.