Not sure if it is a typo, but it's unclear if you prefer USPS (U.S. Postal Service) over UPS (United Parcel Service). For most things, I much prefer UPS over USPS (except when shpg from lower 48 to Alaska or Hawaii, then pricing is better w/ USPS - probably because the higher rates for short trips subsidize shpg to AK and HI). There have got to be good trailer parts folks in NE US that will ship motor freight, UPS, or other.
Most of the trlr folk I know are either in TX or LA, or CA (where my main boat was built).
Champion
www.championtrailers.com lists only UPS on their catalog, but you can call to ask about other options, particularly for int'l shpmnt- 800-229-6690 (not sure if that includes Canada) They do list USPS for AK and HI shpmnts (probably because of rates), but they also charge an extra $10 handling for those.
I'm not sure about their shpg policies, but you can try TrailRite (california) at
714.556.4540