Ray Iles makes carbon steel and D-2 replacement blades for block planes. I have one of the carbon steel blades that I use in a Stanley #18 block plane. It has served me well.
-Andy
I also have a LN in one of mine as they seem to be the only suppliers for the old style with the curved grooves in the back as opposed to the three slots on the newer ones with latteral adjustment.
I also got a Ray Iles high carbon blade in a #18 as well as a Hock high carbon balde in a 60-1/2. I haven't used the Isles blade enough to pass judgement, but I can't say enough good things about the Hock. The Hock takes and holds an edge like no other!
Thanks for the clarification Jason - i've ordered a LN blade direct (and a skew block at the same time - don't know how that worked its way onto the order form!).