[Closed] Garmin mount O'ring - size?

Hi, Does anybody know the size of the large O'rings that come in a standard Garmin bar mount?

I'm trying to mount it to MTB stem, and they have snapped as they are over stretching.

Looking to get some slightly bigger off ebay.

Failing that, can you thread cable tie through underside of the mount, or does it interfere with the quarter turn fastening? (haven't got it to hand to try it).

thanks.