Luka says the stuff in the Black Row is superior to what can be found in the tunnels, and I remember that this used to be true. Not now.
They sell the SecureTekk Jacket (3, 2, 0), the Ares Jacket (4, 3, 1), the Vest with Plates (4, 2, 1) and the Long Coat (4, 3, -2) (ballistics, deflection, dodge)
So the Armor Jacket from Tunnel Guns (5, 3, 0) is better armour unless you really like 1 point of dodge over 1 point of ballistics damage.
I know that we cannot have any of the really nice armour in the Tunnels, and that Luka lies, but I think that the Mars Inc.
Combat Duster (5, 5, -2) for 822 (Armor Jacket costs 756 for the same 4 negotiate char on Normal) would be a nice thing for the store to stock.
It is the top of the line non-hard armour, and made by Mars ...
The NBZ armour pricing is interesting, in that after the Combat Duster, the next expensive thing you can buy from a store (as opposed to ladder rewards, and also not counting Hund Armour) is a SecureTekk Coat (also from Mars) (4, 4, -1) costs 3801 and is Hard. Is 3801 too expensive for a Black Row item? If not, it would be another nice thing to stock, since the proprietor of Tunnel Guns tells you about Hard armour (which he doesn't stock).