I'd assume some electrical supply dealer or online. Bulk LED strip is what's mentioned in that post...
Many a site popped up on a google search of Bulk LED strip and this looked like a good start if you want to just order them online
Edit: added reference to the referenced post
2013 F150 XTR 4X4 EcoBoost SCrew Blue Flame 157", 3.73 - - - MaxTow Retro'd tow mirrors, Raptor 3rd brake light, Roll'N'Lock bed cover, 30" single row behind the grille
Plans for level/AAL, tires, and more IN PROGRESS: HID retrofit - OEM chrome housings with EvoX-R projectors and 55W D2S, no LEDs planned, but hey, since when do I stick to a plan?!
Last edited by Jeriko; 07-11-2014 at 12:21 AM.
Reason: adding reference