Switches are Grayhill 56 series, gold & silver plated internally. Mouser & Digikey both carry them, but they're rather spendy at $10-11 ea.
I needed the very small size (the grid is 1" sq.), so had to eat the cost, but if your chassis can accommodate physically larger switches, they'd be less expensive.
I had boards fabricated, rather than try to hand-wire in free air:
