Then look no further than this....
http://www.argos.co.uk/static/Produc...er/7400995.htm
Beware that you can get them for �159 in Curry's and Dixons
Its the same one i have and it comes with a power adaptor I connect to a cigar lighter I have fitted under the saddle for charging the mobile. but also works with 2 AA batteries.
It has a strong suction holder that will stick to the inside of your screen and it works really well
Other more expensive gizmo's like tom tom rider and Garmin quests II are all above the �400 mark