lol...bad ripoff...you do know it was out before magpul got to it?
GP doesn't have it on their website anymore, or at least I can't find it anymore. Pretty sure you can order a magpul one from Brownells if you want.
I have one made by Phase 5 tactical. Its a nice feature but its a bit bulky in the trigger area. So I took it off, might put it back in at a later date.