Used Colt 9mm mag block.
Mag block has the tension screw and drops in from the Bottom (not a pin in but looks like the newer ones).
It also has the deal on the back that works with the stock bolt release to hold the bolt open after the last round with Colt mags.
$125.00 + shipping (USPS Priority @ $5.00) Postal M.O. or Pay-Pal + 3.5%