I hate to see your thread go unanswered.
The plugs are just body plugs/push pins (plastic). They can be found in different sizes at any auto parts store. Usually found around the fasteners/bolts/washer section. You can even get them at a hardware store.
I don't recall the diameter of the holes on the trunk once the spoiler is removed.
If you want to color match them to the color of your car, Dodge dealers sell little spray paint cans of the color of our cars. Just spray them and spray some clearcoat on them before installing them.
Push them into the holes on the trunk, to seal them good you can put a little bit of rtv underneath them before pushing them down flush with the trunk. If the plugs aren't fully tight... the trick is take a piece of hose that fits the pin part of the body plug and push it into it within (inside) the trunk. That way its tight and won't move around.
Sounds a bit complicated but its not. I know visual pictures would help but the How-To thread on this forum on the spoiler plugs is just dead.
Hope that helps
