Ditto on Wallace Woodstock. I ordered a Macoun and Cortland from them this spring. Trees were at least 9/16" caliper, good rootball and about 4' tall. Price was reasonable for what I got (~$27). I don't think they listed the rootstock on their site, but told me they were M7.
Trees are doing well after awaking from dormancy in May. Had to wait a bit for them due to their grounds were still frozen when I ordered, but the trees were in good shape when I got them.
Oh, and Plant Me Green out of Florida has a good selection of pecan trees, along with pears, peaches, and other fruit trees and some berries. Seems like a lot of their products are geared to southern growers, but they do have some items that will grow in northern climes.