Born in the purpleG 15

You need to have Gear Level turned on to unlock this. But if you’re like me and you’ve been playing with it off for your entire playthrough, you can still unlock this.

Once I was a good way into my playthrough I turned Gear Level on and played for an hour or so and managed to collect enough purple gear to fill every slot.

If you have it set so that you can only carry one primary weapon, you will need to switch it to two primaries and fill both slots with purple weapons.