RAM® EZ-Roll'r™ Drill-Down Mount for Garmin eTrex 10, 20 & 30 – RAM Mounts
Amazon.com: DigiCharge Mount Holder for Garmin eTrex 10 20 20x 30 30x Touch 25 35 Bracket for Mounting On to Bike Handle Bar Golf Trolley Buggy etc. : Electronics
DIY Bicycle Mount for GPS Garmin Etrex 10, 20 and 30. (maybe Other Models Too!) : 5 Steps - Instructables