We've bought a trailer from a dealer in Idaho and the ealer handled the paperwork and collected the fees for us living in Montana. we also bought a trailer in Florida from an individual, did the paperwork together for buying the trailer at a ban, and the seller took care of temporary Florida tags for getting home to Montana, then we registered it once we got home to Montana.
Most dealers are accustomed to selling to buyers from other states. Ask the dealer, if you're using one.
Another option is to set up an LLC in a tax-friendly state and make that the "residence" of the trailer. Read more here: https://www.49dollarmontanaregisteredagent.com/