1995 Jeep Grand Cherokee tow light wiring

1995 Jeep Grand Cherokee mileage: 91,000. My Jeep does not have the factory trailer wiring package. I would like to use one of the new T adaptor harnesses, but the part numbers for these models list for about $70! And appear to require a "power converter". I wired a bunch of vehicles for trailers during my time in a boat shop back in college, what could be so different about today's wiring? Is it just the separate turn signal lamp? Any alternatives short of the $70 solution? I would really appreciate your comment and input before I start probing around with a test light!