bumper pull travel trailer with generator prep/ecnlosure?

Looks like outdoors just has a small shelf on the back for a small generator.

Nash is cool, but it's an LP generator.

I'm looking for something I can fit an Onan 4.0 on board and maybe have a 20-40 gallon tank on board for longer trips. What I would like to get away from is having to carry gas cans and fill the generator often. The Wolf Pack has this, but we don't really need a toy hauler.