The problem with bevel gears and in particular spiral cut bevel gears is the huge lateral loads they put onto the supports. This requires a chunky gearbox with heavy bearings. If you are planning to use this gearbox for a spinner, the tough supports and big bearings are what youd want anyway.
If youre using it for anything else though I can think of some lighter alternatives Only thing is they would take up more space and are probably not as robust.
1. Universal joints. you would probably need at least three joints in series, with bearings supporting the intermediate shafts.
2. flexible shaft:http://www.lara.com/cgi-bin/store/commerce.cgi?oc=WI-FDhttp://www.lara.com/cgi-bin/store/commerce.cgi?oc=WI-FD
They would probably take the torque and might even allow a bit of cushioning to pretect the mag from impact torques. You might have a problem with them whipping so youd have to support them along their length. This would take space but not much weight.
3. polyurethane belts twisting through 90. This could work well and be light. 8mm belt around 80mm pulleys should be able take the torque.