locking lugnut

Ok here's the story. Dropped the car off off at body shopped and picked it up later at night. left key and coilover adjusters in car. well i seen the adjusters in the car when i picked it up and assumed the key was there. it wasnt and body shop said it was in the car. ok the key is nothing more then a allen wrench so i went to grainger tried every allen wrench they had. 10mm a little to small and 12mm a little to big. so where do i get a 11mm allen wrench at? or does anyone have the same lugnuts and can tell me where they got them

Could this be an 7/16"? Real close to 11 mm.

ya, outside the US a bolt that's a standard size rather than Metric would make a quite effective lock