Sorry to resurrect an old thread, but recently True Temper made a run of 44mm steel head-tubes and I figured that this thread is a better choice than starting a new one. See this thread on MTBR.com for more information (warning, Mountain Bike Content) http://forums.mtbr.com/showthread.php?t=617931

Walt Wehner of http://www.waltworks.com has some steel 44mm head tubes in stock now. He is also selling tubing direct to other frame builders. You can get one of these tubes built into a bike by Walt or by Sean of http://www.vertigocycles.com/ and probably quite a few other builders at this point.

The custom drawn tubing is/should-be cheaper and lighter than most lathe milled pieces, although since it is designed for long-travel mountain-bike usage it is probably heavier than something optimized for road bike use.

Disclaimer: I'm a customer of Walt's but have no relationship other than that. He's currently building me a 44HT full-suspension mountain bike with this tubing.