Personally I like the Travoy, especially becouse it works so well without a bike too but I do not like the idea of conecting a trailer (or a bag) to the top of the seatpost of a folder on a regular basis and tow heavy loads fom it. I would look for one that atatches to the rack (Andersen) or the rear axel (Carry Freedom City).

Also there is the Carry Freedom Leaf: https://www.google.no/search?q=Carry...w=1292&bih=657

Couplings and Coupling studs - Andersen Shopper® Manufaktur