Another option would be to get a ring terminal, say 1/4" hole, crimp it to the aligator clip. Now take a screw with some fender washers and wing nut, put the screw through the ring terminal and fasten to the grate, next bend the ring terminal to 90 degrees so it sits up like Tulse's and your done.
Seems like a lot but once you get it done it is easy removed and usable on other grates.
Just a thought after seeing Tulse's pic
Ok after pondering this for a second you could also take a short piece of bare metal I am thinking uncoated coat hanger and crimp the ring terminal to that then also crimp it to the alligator clip and do all your bending with that. again just a thought.
I want a Weber 1880.