Hehe, well _thats_ funny!
I'd suggest to bend a pice of brick-strip to an L-shape, with the short part beeing long enough to act as a key. This way you will experience less interference with the shackle(and the key on it

, have i mentioned this is funny?). Then you should be able to cut a key modeled after the original one, utilizing a rotary-tool (e.g. dremel). I'd suggest using cutting wheels instead of grinding stones for this job. This could take some time as the brick strip is quite hard. Remember to wear safty glasses and let the speed of the tool do the work.
wtf|pickproof?