When I switched from the Midway Guide Pants, which have rather decent knee pads, to the Corrugate Guide Pants, which do not, I missed those pads immensely. I like First Lite stuff, but I wish more of their pants had pads.
Got mine at Home Depot for about $15. The are black with velcro straps and white plastic caps. Colored the white plastic caps with a jumbo black magic marker then set knee pads outside for a couple of days to loose the majic marker scent. They work well.