99harleykins, It’s on the bottom of the tank on the left side.
J B Weld makes something called water weld that will seal fuel tanks, etc. it will seal, plastic, metal, etc.
You could press this around the nut to lock it in place and go from there. It is epoxy so once it sets up you should be good to go.
WaterWeld will plug or seal leaks and patch holes and cracks in almost anything.
www.jbweld.com