Personally my advice is to forget anything with suction. It *will* fail, and it *will* fail catastrophically. And having a corner edge of a smartphone to your 'nads might be a brief distraction from following your route, but it's not really compensation.
I have a magnetic holder which clips onto the vent, and came with a metal disc that can either be stuck to your phone/case or (in my case) slipping inside the back of the case.