I have a custom paint job, no problem, it's magnetic and has a cover for your tank.For myself. My paint is too expensive. I would buy a GPS.
But here are a few http://www.eglidegoodies.com/id191.html.
Just got it and it will not fit the tank properly so will be sending it back for a refund and will keep looking for a bag that will work.I think I will try this one, Ortlieb Waterproof Tank Bag