The pants were plain swat-grey colored pants with cargo pockets sewn onto the outside thigh area. Try to find cargo pants or military BDU pants that look similar and modify the side pockets. You might want to buy two pairs of pants, cannibalizing the second pair for cloth that will make the proper sized thigh pockets.
The pockets on the side of the pants were fairly large, and very reminicscent of modern day Military BDU pants. Depending on a persons size, I estimate the pockets to be 6 -to- 8 inches wide and 9 -to- 10 inches tall. See the Reference Pictures section for more images of the ILM pants.
The boots look to be 11 inch tall black work boots, or possibly "Engineer" boots. Definitely not hiking boots. German Jack Boots would Work well for this costume too.
I would recommend finding a boot that is fairly flat across the top of the boot, alot of the boots out there have a "V" shape to the top of the boot. Also, be aware of the buckle and strap on the outside of the boot. Engineeer Boots have this buckle, but they also have a strap across the bridge of the foot. No one has identified what brand of boot ILM equiped their actors with.
To the left is an image of the type of Boots I wore with my costume (1999-2004).