Lots of people mail order them. The knowledgeable folks over in the Fruit and Orchards forum often recommend Adams County Nursery and Cummins for the east. I have ordered trees from Adams County and have been pleased. You can pick your variety and root stock best suited for your soil and needs. Shipping is expensive for a small number of trees, but mine have grown very well.

If mail order my experience has been to make sure you are ordering from a nursery that has the same climate as you. My only big fail on new trees was the one time I bought trees (bare root) from a nursery in a warmer zone even though the trees were officially rated for my Zone 4.

Trees usually are shipped bare root in the spring or fall when the trees or plants are dormant.

Other fruit and nut tree options like red, white and black currants, also elderberries which grow quickly. They can bare fruit in their second year with the right soil conditions.

Nut trees you will have to wait a few more years. Minimum 5 years for hazelnuts and 8 years for black walnuts, heartnuts, butternuts, etc. All very delicious nuts.

Hazelnuts grow more like a 10 foot shrub and the other nuts are shady trees that grow 70 feet tall.

Nanking cherries are great to eat, mulberries and gooseberries too.

This online nursery Little Tree Farm in Nova Scotia, Canada. They have a variety of fruit trees, nut trees and bushes.

Little Tree Farm Website