One option is to take an existing cover to a jewelry store or a trophy store.
Companion custom banjos did an engraved truss rod cover plate for me.
Richie Dotson at Acoustic Box did one like that for me.
'Terry Shue Orbit' 53 min
'Meat Loaf Has Died' 4 hrs
'RIP Fred Geiger' 5 hrs
'Don’t Neglect The Rose' 5 hrs