I've just tried the electrical tape method on an ipod 5, whilst it worked for a while I found the tape was moving around after a while. Eventually settled on a piece of card a little less than 1mm square, about 120gsm held in place by a piece of masking tape dead centre of the round bit, I first tried to glue it place, but that didn't work nor did trying to super glue the original black bit back on that just seemed to disolve.