IME you can find 100% cotton jeans in any store that prides itself on carrying multiple jeans lines, particularly Gap and OldNavy, but also most major department stores that carry several different types of jeans. It's an option like any other, and you should search for 100% cotton jeans. They are not as popular as the stretch ones as a general rule, but the fabric is more sturdy, so it's still valued by people who work wearing jeans; and particularly those who work outdoors, so western-wear or farm stores tend to have a lot of it. (I get a lot of family members asking me to repair jeans that have gone thin in the seat just behind the 4-way seam. That particular type of wear is specific to stretch denim that has been rubbing against the seat of an upholstered office chair; spandex (aka elastane) is very prone to friction breakdown. People who drive a tractor all day don't want that.)
A couple of months ago I was visiting my DS, who is in his late 20s. He says, "Mom, do you think you could take in some pants for me while you're here; I've lost weight." Now, this is my kid who is on the spectrum, and when he lived at home he would not touch blue jeans with a 10ft pole because he thought denim was stiff and uncomfortable, so I didn't expect that I'd be altering jeans, but all 3 pairs he wanted taken in were jeans. I asked what had happened that he was willing to wear jeans now, and he said that the addition of spandex took away the factor that made them uncomfortable.
Just goes to show that one man's trouble is another man's gift.
