Regarding on which platform you are playing on, there is actually a tip to get an “on-level” BadTouch.
If you can play in split screen mode, just load your main character (the one you want a BadTouch for) and go to Sanctuary.
Then load a brand new character as Player 2, give him some cash, and go tipping Moxxi with that guy. As it’s the first time for him to get a Moxxi’s gun, he’ll get the BadTouch. And as Sanctuary is at host’s level (UVHM), the BadTouch will be at your main character level
You can repeat the process until you get THE BadTouch of your dreams
If you can’t play in split screen mode, you’ll need a friend to help you.
Your friend’s character should be at your main character level.
Simply join him in Sanctuary with a brand new guy, ask him for some cash and go tipping Moxxi.
Same causes, same consequences. Repeat until your BadTouch matches your needs.