A nice aluminium case is available on the Pine64 store listed as "ROCKPro64 PREMIUM ALUMINUM CASING".
The Quartz64 model A can be made to fit this case, however some filing of one of the holes is necessary because one of the RockPro64 ports is a type-C, whereas on the Quartz64 model A all of the ports are type As.
Interference between Quartz64 model A and the case as supplied:-
Fitment once the case has been filed:-
Fitment of the other end (no modification necessary):-