I've said it before, but push pins and carriage bolts look like ****. Believe me, I tried them both.
1. Go to a vinyl decal shop (the type that makes decals or signs), and get some pre cut circles a little larger than the holes on the decklid.
2. Paint the circles while still on the paper sheet with touch up paint.
3. Let the paint dry.
4. Carefully peel the circles off the paper sheet.
5. Stick to the trunk lid.
I had my lid this way for years, and you can't even tell until you come really close to the trunk to see that it isn't filled. With the bolts or plugs, you will always see those ugly lumps on the trunk.