The only place you can buy these is at the Dealer :(
Cuz i know like me, i need my bonne for work so i could not wait for GM PD ro ship them.
It will run you about $10 each for each part, the Retainer and the Insulator.
So $40 for each side $80 total or so.... give or take $2 a part
Heres a pic of the parts. just bring this with you and they will know what to get you.
And like me, you really dont have to replace the top parts unless they look really bad, mine didn;t look that bad only the Bottom ones did.