My Type R spoiler, Please Help

I bought a type R spoiler awhile back, and I just got it painted. When I went to have it mounted on, they said there should be some rubber peice that goes in between the car and the spoiler. Almost like a small rectangular peice of rubber. Now I am almost sure that my spoiler did not come with any. Does anyone know exactly what I need and where can I get it?

please:)

Its a cushion, right? You can buy some at a crafts store or a hard ware store. Even double sided tape should work.