have a look at aminet, i'm sure this hack is there. it will tell you what diode (probably any 'ordinary') and which pins.
floppy power has +5 and +12 volts, be careful not to 'overload it' by taking too much current. don't try to get 7Volts (12-5), you might damage something.
you need some 'DC to DC converter' to get other voltages.