I don't know of any nursery in NE that has a "variety" of dwarf hemlocks. Why do you want these? Do you get wooly adelgid in your area/zone? Most retail nurseries like Weston Nurseries or Bigelows get their conifers from Iseli in Oregon.

http://www.iselinursery.com/

Steve

You may be cold enough that wooly adelgid are not an issue. If they are, consider Japanese Hemlock, hardy to to at least z5, maybe z4. Weston Nurseries in MA sometimes carries the cultivar 'Loowit', which stays dwarf.

http://westonnurseries.com/Plant/tsuga-diversifolia-loowit/

If wooly adelgid is not an issue, Broken Arrow Nursery has 'Moon Frost', which is a really nice dwarf variety of Canadian hemlock, and they ship.

http://www.brokenarrownursery.com/shop-online/evergreen-conifers/tsuga/tsuga-canadensis-moon-frost-moon-frost-eastern-hemlock.html