Some Levis have stretch fabric - I buy 514s, there may be others. Make sure that the label calls out the stretch material.
Thought that was an unfortunate typo - I wear the 541 Athletic Fit Stretch jeans, and remember the 514 as the old, constricting straight fit. But apparently they're making 514s on stretch now, too.
I rock the stretch 511's as my daily wear these days. I have large calves and thighs and while the fabric does rub it also gives me my full range of motion. I wouldn't want to work out in these things, but I probably could if I had to.
Prana and north face have some good stuff. You might want to watch for sales, but super comfy.