Help! cute sweatpants!

Hey. I know a lot of people think that sweats look frumpy and i know some people like the look if you can dress it right. I saw some girls yesterday who were wearing sweat pants, not the fitted kind that form to your leg, but the kind that are loose all the way through but only tight on the waist, like there was an elastic band there. They wore them low on their hips with a cute lacy pink tank top and i thought the look was adorable. I already have tanks like that so all i really need to know is where to find these sweat pants. They were plain black. They looked like they may be men's sweatpants but i thought the look was cute and i would like to try it. If you know what sweats i am talking about PLEASE let me know of any stores to buy them at. Thanks! xxo