You can use a soda can, aluminum sheeting/flashing, really any conductive material that is fairly rigid but still flexible. The design is the same as Hellfire's simple switch design as documented here:
http://www.hellfiredrums.com/archives/67 If you happen to convert acoustic cymbals you can use the actual cymbal as 1/2 of the switch and further simplify it. Basically what's documented is two of these switches, one on the top surface of the edge, one on the top surface of the bell. I've only used them on the bottom surface of the edge as a choke switch but it should be completely effective as documented.
Here's basically the same thing (top mounted switch) documented clearly in English here:
http://www.vdrums.com/forum/showthread. ... e+hellfire And the OP actually used an acoustic cymbal and made the switch blend in fairly well so it's not completely unsightly.