You can make a 12mm tool that will slip into the tool box.
Get a 12mm bolt, that is 12mm the size of the head not the shank,
And two 12mm nuts and some strong bond thread locker.
Put thread locker on the bolt, tighten down the two nuts and tighten them together.
The insert the bolt head into the axle, turning the nut that is closer to the bolt head to loosen the axle.
Let it sit and it should work to remove your wheel in a pinch.
Look for a bolt with the tallest 12mm head on it.
The other option is ordering a threaded 12 mm standoff in metric.
There are also folks who sell 12mm hex sections that do the same deal.
Last edited by Squish; 03-17-2014 at 10:33 AM.