I have an apple, crabapple, and a couple black walnut trees that I got from a place in NY state - St. Lawrence Nurseries. They are on the border of zones 3 and 4, like us. They don't baby their stock at all, so it's used to our type of climate. Their bareroot prices aren't bad either. I read a really good book on home orchards in MN, and they seemed to be of the opinion that a lot of nursery stock trees are really babied and often come from another hardiness zone. So say your pear tree is hardy to zone 4, but it was raised in zone 6 - it will not be nearly as tough as a little tree that was raised in zone 4. If you're having bad luck with trees, maybe keep that in mind as you shop around and ask questions. I literally stuck these in the ground and just watered the first year. No maintenance besides cages to keep the deer from eating them in winter. The bareroot ones will take a few years to bear. Now, I'm not calling you old, but the upside to a potted nursery tree is that they often bear sooner. So maybe something potted but grown around here?? Good luck with the pear tree shopping!
Well, the sun came out over here yesterday afternoon. Sunny again today!
Have a good day, all ~