Any chance that one could just take one of those LED trailer taillights and adapt it to fit inside an LX or GT lens housing? Y'know, take off the plastic shell that those come with, figure which wire goes for the parking lamps and which is for the brake lamps, and then secure them behind the LX lens...? You can score a pair from Harbor Freight or AutoZone for pretty cheap.
That, or taking one of the aforementioned OEM LED taillights and trimming it down to fit ... although that'd be a way more expensive way to go, I figure.