I'd say your best bet is to go ahead and build one youself. You will probably not be able to remove it (without bruteforce), but I dont think you are in luck finding someone who has a spare cap.
You can build a new cap from spare plastic sheeting. If you dont already have that, then you could probably use what you find in CD cases and DVDs.
If done right it will look better than the hole you have right now
Tony Fisher wrote:
I believe it would work best with black plastic.
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