Here is a 3d printable design of the Magpul AR15 extended BAD Lever.
Lets You Release The Bolt With The Trigger Finger; Improves Readiness & Efficiency
The Battery Assist Device (B.A.D.) is an extended bolt release that allows the shooter to keep his hand in the ready position on the pistol grip and operate the bolt catch with the trigger finger. Streamlines bolt catch manipulation to get the weapon into battery more quickly for improved operator readiness and weapon handling efficiency. Easy to install and remove—no weapon disassembly required. The B.A.D. lever clamps securely to the factory bolt release and extends a paddle through the front of the triggerguard to the right-hand side of the weapon. Trigger finger can stay outside the triggerguard as you operate the lever, and factory bolt catch retains normal function with B.A.D. installed. Originally printed on a XYZprinting Da Vinci 1.0 3D Printer, Grey
Check out the design, download and print it from grabcad here https://grabcad.com/library/extended-bolt-release-ar15