While I can't recommend any vendor I've never bought from, and you'll have to do your own research to confirm that its the correct part you're looking for - it appears this vendor has a lot of parts for the ROG, including a waitlist for what looks like the correct board:[br]
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https://en.accessoires-asus.com/ally-console/ally-spare-parts/asus-left-joystick-controller-board-73891-111688.htm[br]
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Again, I don't know the internals for that device and I have no experience what-so-ever with the vendor but thought I'd offer what I saw.