You could order the part number easily enough from Tesla. As said above fitting it would mean it would work briefly when your car boots up, but stop working once it realises it's not part of the spec (like ambient lights on SR+).
Given my recent experience trying to get my heated steering wheel working on my 2020 car, I would be surprised if there isn't some internal "script" that Tesla could use to push Boombox to the car's gateway configuration. Getting them to do it is the hard part as there's no official retrofit in the UK.
It looks super simple to fit from the service manual, so you might have more luck buying it, fitting it yourself and then pitching up at a service centre saying "my PWS isn't working". A bit devious but..
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