Field clothes for working preggo

Aj

I need maternity pants for working out in the field on hot days! Rough n' tough jeans or khakis, or cargo pants or trail pants or SOMETHING! Where to buy??!?!?!

All the maternity clothes I find are all super nice jeans or in-office work clothes and I need something I can wear to literally get down and dirty in (I'm talking tall grass, water, mud) without having my stomach crunched in all day!