I'll second the recommendation of Skillers Pants. I've used them since the '80s. Slide the pads into the builtin pockets of the pants, when needed. There are no circulation cutting straps holding them in place. (Big win, that one, for my legs).
I saw the Skillers in the Deluth catalog and I was wondering if they are hot. They look pretty thick. If they are no hotter than baggy Levi's I could live with that. I see Deluth also has some nice kneepads with a liquid gel in them for around $80.00. Big B in AZ.
I can't bring myself to spend more than $20 for a pair of jeans. I'm glad the Skillers are working for you guys, though...
As fo knee pads: -I found that I slid around too much with the "hard cap" type. -Nylon-wrapped foam rubber (the AWP brand from Lowes) has worked very well for me, and they are affordable. -If I needed more protection, I would look at the "tactical" ones (see www.actiongear.com). They have stout rubber cups over the foam lining.
Heck, after last week's crawl space, I'm also considering elbow pads!