A Dixmor LED7 should fit in this plastic box:
https://www.homedepot.com/p/4-in-x-4-in-x-4-in-Junction-Box-R5133709/202043437
Some stainless security screws will keep it safe. It may not look nice, but it'll work. Laurel Metal makes boxes for a LED7 and a card reader, maybe they make a box...