I have a Pro 58 that refuses to stay on the windshield, keeps falling off. I recently bought some new suctions cups at Walmart that were very close to the orginals that came with the unit. Didn't last long before they fizzled out. Does anyone know where I can get some good ones that will hold? Or does anyone know any tricks that help suction cups keep a firm grasp? This falling off the windshield is getting old real fast. Thanks.