I have a nice back glass but there is no mask at all. I tried to find a decal but haven't had any luck, so making one yourself may be the only option (which shouldn't be too hard with Tim's help). As you probably know, the glass itself is very difficult to find.
PM me if you're interested and I can get you some pics. I can also bring it to MGC (Saturday only) so you (and I) won't have to worry about shipping.