Sorry, I got very caught up in my Batman costume and have been mainly focused on that lately. No new progress. As far as I know, regarding pants, I would say regular OD green Army pants, perhaps spray misted with a bit of brown would work well.
Well i am still working on the project, and i did a bit more research and found a pair of pants that would work well for the regular NCR troop, maybe even a 1st recon. I found the pants on the same website you found the coat tk-1776...