For cold or cold/wet, I use wool. For a pant you can wear to the office try ex military wool serge or twill uniform pants. I haven't bought any recently, but they used to be available cheap and in near new shape (no one wears a dress uniform very often any more).

For warm or warm wet I still use denim. I am not comfortable with nylon around fire and Nomex is too expensive. I did once have a pair of Cordura coveralls (to cover my dive suit in nasty places) that would have made very rugged pants, but was never able to find any of that weight.

Respectfully,

Jerry