I need it for my Pikachu but I'm not sure if I can get it anywhere. Some sources said it was a gen IV item and some said gen II; please help.
No you can't, you'll have to trade it from Ruby/Sapphire/Emerald.
As for the sources saying Gen II and IV it was originally released in Gen II but Gen IV it was somewhat easier to obtain.
You can only get one through trading a Pokemon holding one from R/S/E. In R/S/E there is a 5% chance of getting them on a wild Pikachu.