Highlander tow ratings range from 1500 pounds to 5000 pounds depending on year and equipment. Start by reviewing the towing section of your owner's manual. If necessary, a dealer can use the VIN
to determine what equipment yours has. Some things can be upgraded aftermarket, but not all.
Once you know the tow rating of your vehicle, the thread "Trailer Weights in the Real World" in the General Chat section has some good data on what different fiberglass trailers weigh once you load them up. Post #297 links to a spreadsheet.
That'll help you narrow down your search.
Best wishes in your "egg hunt"!