If this Sunday works for you, you can get your rootstock at the Seattle Fruit Tree Society/ Western Cascade Fruit Society spring fruit and grafting show- March 14, starts at 10am (ends at 3, but I suggest going early so you can see the presentations); location is the Center for Urban Horticulture in Seattle. There is a minimal charge ($3-4)for rootstocks, and I think you can get up to 5 scions for free, then $1 each after that (there will likely be a good variety of apple types). I'm headed there to get scions to try my hand at cleft grafting onto a old/bad cider apple tree, in the hopes that I can get something useful out of it instead of digging it out. Hope that helps!
Keith

Seattle is a bit of a drive for me on Sunday. Thanks for the tip, but am looking more in the Tacoma Pierce County Area for Rootstocks.