Lutefisk and lefse
Nordic Delicacies will deliver.
Nordic Preserves Fish & Wildlife is great, but I've never seen lutefisk there. Nordic Delicacies is the only place in the city I've ever seen it, in fact.
You might also check with a couple of the Scandinavian churches - the Norwegian Seamen's Church in Midtown has a little store, as I recall. There's also a little cafe in the Swedish Church on 48th - if they serve lutefisk, you might ask them where they source theirs from.