If you are handy with tools you may be able to make the parts of the guard shown below and take to a local welding shop for final assembly and heat treating:
(1) The guard shown above requires no padlocks of any kind because it is attached to side of house or garage by means of carriage bolts, 
which have smooth round heads and pass through the wall. They can only be loosened from inside the house or from inside a locked garage. The carriage bolt is shown at right.
(2) The guard suggested here is designed to give you the same control over access to your meter that is already enjoyed by many homes and businesses that have meters located inside the structure.