screws usually come with the headunit, but if they didnt, id drop into yuor nearest audio installer and just ask. i usually give them to people for nothing.
I did that they gave me 4 that fit for $2 bucks alas they're not flat on the top and protrude out. I can FORCE the bracket/head unit in but then it pushes on the sides of the cage enough that I cant get the 4 dash screws in!
GRRRRRRRR!
Basically I'm going to need the same screws with a flat top and hope they're not thick enough to push on the dash cage