Rear Numberlplate grommets?

[Johnnywb]

All,

Just replaced the rear plate on my car with my personal plate. When i removed it, one screw came out ok, then the plate fell off the car...

In the bootlid, there's two rectangular openings with rubber grommets with metal threads through the middle. The numberplate secures to these. One of mine just falls out the hole as the rubber has perished.

Does anyone have a part number or idea on price? I want to know whether it's worth getting another, or just going to halfrauds and getting some velcro to keep it on!