I am watching CL but most of the ads are for new units from dealers. As for the private sellers...I think I know what you mean about having to pay for TTL. I tried to transfer one once and had to pay double as seller had jumped the title.Check Craigslist and FB marketplace. Most of them you'll find the owner wants you to cover their initial tt&l costs which you have to pay again when you register it.
Went looking for used trailers a few times but went with new after shopping around.
Good luck.
I ordered a new one but it won't be ready for 5 months. After that I may be selling my 20' trailer but haven't decided yet.