I believe that they are available, Jeppesens as well, but rather expensive.
A cheaper bet, and legal if its for your own use, is to get them scanned by someone with an A0 scanner (architect's or graphic designers maybe). 100DPI and low colour is quite adequate (about 10MB as a .bmp).
I think the typical cost is about £10 on zip tape, a bit more for CD.
There are a few commercial programs that can give you GPS moving map from these (Fugawi or Oz Explorer).