Some aftermarket product just take time to appear, which can be frustrating. There is a decent selection of vehicle-specific brackets to mount fifth-wheel hitches in a pre-2015 F-150, and the current model is more capable so it should be used even more frequently for fifth-wheel trailers (as seen among Escape 5.0TA owners), but there are no mounting brackets... yet.
I found with previous cars that if you wanted an aftermarket towing hitch when the car was new, then it wasn't yet available. Wait long enough, and the hitch would be out of production. Apparently you need to wait after buying the vehicle, or buy a used vehicle just old enough for the aftermarket to have caught up, but not too long.