Hi Zach,
I would not try to fire up the T3 with 2 r123`s! That`s ~7,4 - 8,4 Volts.
Guess the light will only light up once, for a very short moment and then never again. (without changing the Led.)
May be you can try a 17670. But if at all, it`ll give you a reduced output.
(Sold my T3 and sorrily can`t test it for you.)
My SL TaskLight 2-L Luxeon runs on 17670 but with the already mentioned reduced output.
Wolfgang