punto sporting rear speaker probs

[PAULYB]

hi all hope someone can help i have a 2002 sporting and wanting to change rear speakers the thing is all 10cm speakers have 4xbolt holes but the standard ones have 2x lugs on them that locate them in to the rear speaker shelfs under the grille have looked every were for a 2xluged adpter but can not find one is there anyway to fit new speakers in to this space