A suitably vintage (read: beige) board with NKRO (because it uses capacitive switching) would be a BTC 5339, should you happen to find any in local thrift stores; I found two.
Problem is, they have really mushy keys if you get the ones with springs instead of buckling sleeves. Can't stand it all that much. They also have fat reverse-L Enter keys, but at least Backspace isn't emasculated as a result - the Backslash (/) key is tucked in the corner beneath right Shift and beside right Ctrl for some reason.
Other than that, you might be harder-pressed to find full NKRO options if you're not picking a capacitive board specifically. I'm not sure which Cherry-made boards for PCs have the NKRO diodes, but I'd consider them more likely to include them than most if they're the only ones to ever make an Amiga keyboard with NKRO diodes, which Mitsumi and NMB never bothered with.
As an aside, playing Wing Commander on a keyboard sounds like an exercise in masochism. Do consider setting aside some space for a joystick in the future, maybe a Thrustmaster FCS for period-correctness. (NOT a CH Flightstick Pro or the budget Suncom F-15 stick models; you can't press buttons 1 and 2 on those simultaneously due to chorded button encoding for the hat switches.)