There IS NO factory OEM kit for this. And there's no easy way to retrofit the MY16 parts to a MY14-15 truck that doesn't have the option.
Some here are apparently hell-bent on trying, but the long and short of it is -- even if you did get all the gate parts and pigtail, you'd still have to repin and rewire half of the main body harness.
It's way, way more work and way, WAY more cost to try and do it, and the resulting product won't feel any more or less OEM. It also won't have the warranty that Pop and Lock offers on its kit, for what it's worth.
TL;DR -- just buy the Pop & Lock kit. I assure you, if you take your time and do things patiently, you will have no trouble installing it. There are plenty of resources both on this forum and on YouTube that clearly show how straightforward it is to install.
And yes, splicing/soldering the Pop & Lock harness to the lock circuit is ideal, but even just using the included T-taps properly (i.e. using pliers to apply sufficient force to fully seat/ lock the splice part of the connector instead of trying to do it by hand) works fine. That's what I did on my truck and I've had zero issues in the year-plus it's been on the truck.