i think chad and shmokes have both had a go (in their youth) at fixing em, as have i recently. i have a mad plan to make a bullet proof one, one day

the n64 joys are photo-optic like the old style mouses (meece, mice) so sadly you cant use a joy out of a cheapo modern controller because they all seem to be the resistor type.
but there still seem to be replacement joys around with a bit of looking. i bought one from
these guys and it was fine. i have been using it for a couple of months now and its still good. i couldnt tell if it was BRAND new or not but it feels as if it is. dont get one from a crowd on ebay called gameznetwork. i ordered one from them and it never arrived. then they wouldnt answer my queries until i commenced an action with paypal, THEN they started talking to me. too late, i gave em negative feedback AND got my money back
