Clark Rubber have a range of plugs in grey/black that will suit, I pieced together two "sets" of 5 assorted plugs to fill the holes when I had my wing off for a short while a couple of years ago.

Be sure to buy a third brake light for your rear parcel shelf or you may run the risk of getting yellowed.

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Silver GC8 | RallyArmor
"Perth WRX, home of the cynical." - TROLLEY