Bike wrenches are often flat, but they are usually metric. I believe 11mm is fairly close to 7/16. Park tools have a pretty good reputation.
Maybe try this:
http://www.amazon.com/dp/B001B6LJZW/?tag=atomicindus08-20
Tons of things around a datacenter use that same 751 key, from server cabinets to UPS's. We always kind of thought of those locks as more to prevent casual access in an already secure facility. I can't believe they use them for things that are actually supposed to be theft resistant.
We also...
I had the plug on the remote fail on mine after about 6 months of infrequent use. I replaced it with a 4 pin trailer plug. Just recently the free spool lever got stuck and will not turn, I had to power out to use it.
The paint and the insulation on the wires have sun faded badly, all decals...