I'm pretty sure it's plastic, since it's the same one that they use in Defenders.
Of course, there's nothing WRONG with a plastic trigger per se.
The parts were delivered through CMore/ Colt Comp IIRC. Perhaps you could contact them to find the supplier?
I love the profile of the safety, and on my Defender I got a set of King's Ambi's. They're too wide on teh pad, but you can grind them down to a more managable size. King's also doesn't use the little leg under the grips, instead holding the offside on with a different hammer pin. Looks cleaner IMO.