Warne MEG422BLK Magazine Extension made of 6061-T6 Aluminum with Hardcoat Anodized Black Finish for Glock 42 Magazines (Adds 2rds) $34.99
Rival Arms RA70G001A Mag Baseplate 9mm Luger/40 S&W/357 Sig, Compatible w/Glock (except 36/42/43/48), Black Aluminum $15.16