A few links for you:
http://www.bentrideronline.com/messa...splay.php?f=12
http://recycledrecumbent.com/
http://www.recumbents.com/wisil/whatsup.htm

Nova has a pretty easy to figure out website and was very easy to deal with the one time I needed them. They list steel headtubes in various lengths for 1 in and 1 1/8, some thin walled for lugs, some a bit thicker for fillet or welding. The ID is just a little under finished size, so no boring is needed- just ream when you`re done. If you wanted even thicker wall for MIG welding, I dunno. Probably have to order oversized with monster wall thickness and turn/bore a lot of material out of the way to make your tube.

For somebody who knows, is it really necessarry to use specific headset reamers? Is there any problem with reaming the full length with an adjustable and having a bike shop face the ends?