Hi Bob and welcome to iRV2! Glad you joined us.
First you have to establish the max towing capacity of the Expedition, keeping in mind that any extra weight carried in the tow vehicle, e.g. passengers and gear, has to be subtracted from the max tow rating. With that number established, you can shop for trailed with a GVWR less than the tow capacity.
2004 American Tradition; 2014 Buick LaCRosse
Homebase in the Ocala Nat'l Forest near Ocala, FL