Need help finding a vented panel for server rack

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I purchased a 9U server rack cabinet but this cabinet doesnt have a back panel. Im trying to find a vented panel, prefer similar to what the box already has, to mod onto the back. I need to be able to lock the back but still open it for access so ill be adding hinges, or something similar that's still lockable.

Anyone have any ideas on what I can use to close this cabinet up? Figured this would be the best section to get help.