I have the form in front of me from GL that you fill out and send to them to get a SF97 (filling it out for my M817). It has a section on top for trucks, one on the bottom for trailers. The instructions say to fill it out and return it (signed) and that they will ping your CC for $60 for each vehicle/trailer that you want a SF97 for (or you send them a MO or Certified Check) and they send you the SF97. They caution that incomplete forms will be delayed as they have to have complete info (can't send out a SF97 with missing info) and that incorrect data will cause delays and problems getting titles from states if you have an incorrect SF97. No where does it say that you have to have the form filled out by a LEO... Fill it out yourself... It says "I am attaching information requred to complete a SF97, which I have either personally verified by inspection or had an inspection completed..."
Now, a few notes about trialer tags in my state since it sounds like yours takes a similar view of things...
In NC, you have to title trailers and you put tags on them as well (got to have a title before you can register it and get tags...). Need a SF97 from GL if you purchased from them...
If you purchased a trialer at Home Depot (in a box or assembled), you get to take your Home Depot Bill of Sale down to the tag/title place and you get to attach a VIN tag to your trailer in additiion to the regular trailer tag... They will either state the manufacturer as the folks who made the kit or call it homebuilt depending on who pushes the paperwork.
In NC, the Permenent tag fee is same as five years of annual tag, if you keep a trailer at least five years, permenant tag is less expensive. Same tag fee for all trailers regardless of weight since towing vehicle has to have a tag that has enough declared weight to cover the GVCW of the combination at the time you are checked (if you are...).