Rig Hand have you given any thought to installing a lock bell? We place them over padlocks on tool vans all the time. Please excuse the crud drawing, nothing more than a 1/2 or 2/3 of a piece of pipe or square tube. Anything with just enough height to allow your hand in with key to unlock, but prevents bolt cutters or 24 inch pipe / crescent wrenches from getting to the padlock!
You could easily cut / rip a piece of pipe weld a backing plate to it on the backside, and tack it to the lead well cover. Then a thief would need a torch to get to your leads!