Robert Hall at
http://www.xblights.net/products.html has very nicely made taillight asemblies, with very bright LED's. Options 1-4 are running light/brake light only, the rest have integrated indicators; the cover lens can be white or red; a standard option (no add'l charge) is also to set up several LED's at the bottom of the assembly, with part of the lens being clear, to illuminate your plate. To save some on the cost, he will make yours using your OEM taillight.
They are not US DOT approved. No idea how any such aftermarket product would be, unless imprinted with "MOT/DOT Approved." But one sees many such items out there, so either they are passing inspection, or riders replace some items with OEM just prior to inspection time....
As the base of the assembly is the OEM part, and since he has no need of your red lens cover, you could always keep it to put in place of his lens when inspection time comes around. I would never do such a thing, just as I only ever ride over 55 mph on a closed racetrack circuit
