I just returned from a 160 mile-ish trip through the central UP and saw three teardrops (none at the campground I stayed at, but there were only six sites at that lake).
I don't count the big commercial teardrop shaped units that are getting more common. Just Benroy and similar designs with sleeping cabin and galley hatch on the rear. Hard to tell manufactured from home built since there are some very talented home-builders. Central Wisconsin seems have a number of manufacturers such as Camp Inn and TC Teardrops. I think that adds to the number seen; including inspired home-builders.
I've tried to inspire small gatherings in the UP, but, it seems that there is a lack of folks interested in that in this area (or, I am not very inspirational). The St Croix chapter (WI/MN) and the Great Lakes chapter (MI) of Tearjerkers seem to focus on southwestern WI and MN and lower Michigan with their gatherings and mostly do it informally with the occasional biggie like the Camp Inn Camp Out.