Michigan will do permanent plates for out of state residents for trailers. Takes an inspection and 3 years plate fees. I'm planning to do it soon with my trailer as 3x MI fees is only about 130% of Ohios fees. Do contact your insurer and look up the local rules, regulations, and laws about out of state registrations before attempting (though due to commercial interests there are rarely laws regarding trailers with out of state plates, only likely to be an issue if your state has a specific section regarding non-commercial trailers)