Just thought I would share this, i know theres probably been a million threads about phone mounts or whatever, but this is just a simple cheap solution to the problem. I need to use GPS often, living in the bay area its almost a must.
Ram mounts or similar mounts seem too costy, i'd rather spend money on something else. and i did actually construct a device out of PVC pipe that works too. but this is sleeker, and way easier.
Just buy this Phone/GPS mount, made by Scosche. I bought mine at Walmart for $22. Model #: IUHW9R
The attachment for the suction cup has a little screw where it's secured near the top, just unscrew that and take off the bendy stem and suction cup piece. you're left with a round nub, this is the exact size you need to insert into the steering head mount. it fits nice and snug, and doesnt budge at all. it even swivels aroundso you can position it however you want.
The part the grabs on to the phone is nice and sturdy too, locks in your phone or gps. And its in the little air bubble so its not constantly being hit by wind.
Just thought I'd share this since it helped me out.

 

Subbing in to remind me to try this later. I've got one laying around I wanna try.