I searched high and low for a decent pair of working pants that can handle the bending, stooping and kneeling of prospecting. Military fatigues were close, but too many knockoffs and they weren't holding up. A few months ago I began an online search and came up with some real winners. Mind you, I have no vested interest in the company, no affiliation whatsoever, but I thought I would share my knowledge. I bought 1 pair just to try them out. They were so comfortable, I bought 3 more pairs and they are now my everyday pants, not just prospecting.
The company is Duluth Trading, the pants are called "firehose flex". They make a bunch of other working pants, but these seemed right for my purpose. Not cheap, but so far well worth the money for me. The key is they are looser in the legs and have a gusseted crotch. Now I'm not bragging that a man like me needs that extra crotch room, but they really make a difference for bending and crouching. They are pretty lightweight, probably not warm enough for colder climates, but I think they make some with a lining. I bought some for my 21 yr old son, he's a lot leaner and fitter than his old dad, so he wasn't that fond of them. Oh well, its the thought that counts. I'm not trying to spam you, just passing on some information I wish I'd had a couple years ago.