Thanks.
The only external antenna listed by Garmin for the Aera 500 is the GA 25, and that comes with magnets, although they can be removed.
Garmin do list the GA 26/27 suction mount, on the same page, and looking at the bolt holes in the picture, I think they might fit the GA 25. I will give it a try.
== updated ==
I called Garmin, and apparently the GA 27C (MCX connector) is the antenna to go for, despite their web page.
Last edited by 24Carrot; 18th Feb 2011 at 12:58.
Reason: Called Garmin...