Not sure of where to get one here in Canada but I've been using a dial caliper. Its not exactly the best thing for something intended for measuring but its temporary. I've been saying that for a while. Lol. I do want to make one to see how it works out. Maby this weekend.
As Icho said, you can make one. Or you can do what I do: Take a drill bit, the same size as your steel (e.g. 5/16" steel, use a 5/16" drill bit). Clamp the drill bit to your bench or other flat surface. Put some black marker on your steel where your edge will be. Slide the steel along the point of the drill bit. That should give you a nice scribe line down the centre.
r-ice, I have been making these for years and have a few left if you are interested pm me and I will get in touch with you.
I use both of the tools shown here by forge. Picked them up from him this winter and they work great. I especially like the grind height scribe since sometimes its tough to get the even by eye or by measuring, but this gives a perfect line on each side.
I too have one of these 'FORGE' masterpieces !! works good..............havent heard from him in a long , good to see him back !!