Your EagleTac may already be the brightest stock 2xAA. Other than Quark 2xAAs, your best bet might be to get a 3xAA Dereelight host and order a Neutral White XP-G from NailBender, equipped with his 3.6V-8V driver.
Thrunite and Dereelight each sells a neutral-white XP-G that is driven at 1.5V for a nomina rating at 493 lumens. I can't keep straight whose model is regulated at what voltage. Thrunite had to clarify that his 2.7-9V version won't be regulated below 3.7V. I'm hopeful that that means it will deliver full regulated power with three NiZn AA cells (4.8V).