RAM Part RAM-B-174-MA4U : Manufactured of heavy duty aluminum.  These mounts are arguably the best made for motorcycle use.  No modification to your radio is needed to use this heavy duty metal mount.  This mount attaches to the back of the cradle that came with your GPS.

Fits many models including:

Audiovox XCS9, Audiovox Xpress EZ, Audiovox Xpress R, Audiovox Xpress RC, CommanderMT, Delphi Myfi, Delphi Roady, Delphi Roady XT, Delphi Roady2, Delphi Skyfi, Delphi Skyfi2, Delphi Skyfi3, Mirge, onyX, Pioneer Inno, Pioneer Inno2, Samsung Helix, Samsung Nexus, Sportscaster, XMP3, XMP3i, Xpress EZ, XpressR, XpressRC, XpressRCi