ProtoDoc,
I see you're in NYC.
You had quite a selection of nail hard, tough pants over at Canal Jean... Alas, the icon of Soho shopping has gone the way of the Dodo. (they do have a Brooklyn store, but I have no idea where it is and how to get there)
Now, your only options left are IceBerg on Broadway, Dave's on 6th Avenue and some place on Broadway a few blocks below Canal Street.
Your best bet is the Carharrt pants made of heavy cotton duck, the same stuff as their work jackets. They're made in a variety of styles that should suit most of your casual and work needs. However, as you visit these stores, you can browse the other brands and see what strikes your fancy.