The portable toilets seem to be the more common equipment sources in this game, so if there is a area with a lot of them you could load game, collect, quit, wash, rinse, repeat. I don't have a specific area in mind though. the one by the starting outpost is relatively easy to get to, and poorly defended. However, it is only one outhouse.
The Dry Docks in Three Horn Divide has a red chest, a long chest, and a toilet that you can get by just running in. All loot is level 13, I decked out all my characters and my friends characters at level 13 there.