Barre Trash's Trashbag Shorts 2.0 are here. Updated to have a drawstring leg-opening (no more elastic), for an adjustable fit. They've also upgraded the fabric and the logo printing for better durability. 

Barre Trash works with a factory that exclusively makes dancewear (for the biggest European brands) to create a trash bag short that moves with you, keeps you warm, and doesn't get in the way.