You can find the Phase 5 Oversized Magazine Release (OMR) Black here.
The Phase 5 Oversized Magazine Release (OMR) is a drop-in two-piece replacement for the Mil-Spec magazine release. Machined from 6061-T6 billet aluminum to be lightweight yet strong. The easy installation requires no gunsmithing or special tools. Color: Black Features: Larger contact surface than a Mil-Spec magazine release button Ergonomic pocket on the surface of the paddle for your finger CNC machined from lightweight 6061-T6 billet aluminum for strength Compatible with Extended Bolt Releases Compatible with anti-rotation trigger/hammer pin sets Fits AR 5.56/.223 and 7.62/.308 receivers