Other than buying an aluminum case and doing the metal work to cut out the front and back faceplates, no actual suggestions on the case.? I prefer metal for the RF shielding as the uBITX is noisy and susceptible to external interference.
The post is to remind you that there is a significant difference in the current requirement of the 7" vs 2.8" Nextion display.
7" - 430ma
2.8" - 65ms
The 7" display will need a separate 5volt power source.