I'm only throwing this in since you haven't had any replies here, but doubt I will be of any help either.
Firstly, what do you mean by "blanks"? Are you talking about steel that's already roughly profiled/shaped into a knife blade? If so, I don't know of anyone that offers them in real L6, but either way we'd need to know what kind of shape/size you're looking for.
If you just mean flat bars of steel, then Carpenter does offer L6 in flat bar form. However, so far as I'm aware, the thinnest they make it in is 3/8" thick. Crucible also offers their own formula of L6, but they primarily make it in round bar stock. I spent hours & days searching for L6 stock in 1/4" thickness, and finally just bought some thicker stuff & had a reputable smith forge it down for me. I can provide his name if you're interested in pursuing that route.
Then again, if you give us a better idea exactly what you want to make with it, it's possible there may be other steels that are actually more suited to your purpose & easier to get. I'm sure the guys in the shoptalk section could give pointers from that end as well.
