Amazon carries StarTech and Tripp Lite branded recessing adapters and front panels.

Recessing bracket: https://www.amazon.com/StarTech-com-Server-Rack-Depth-Extender/dp/B01GGKM4S8/ref=sr_1_3?dchild=1&keywords=Recessed%2BRack%2BAdapter%2B-%2BRack%2BMount%2BAdapter%2BKit&qid=1615498597&sr=8-3&th=1

Front panel with key lock: https://www.amazon.com/StarTech-com-Rack-Mount-Security-Cover-Compatible/dp/B084PBTJ7J/ref=sr_1_4?dchild=1&keywords=3U+rack+mount+front+panel&qid=1615498953&sr=8-4

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Note: IT rack standard cage nuts will be required.

Yeah, I was in a similar situation, even bought that extender you mention and these startech 1U and 2U variant, but they don't fully align with 1U/2U stuff like switches, patch panels and servers, so I replaced it with a deeper rack, problem solved.