Sport Elastic - 1.25" wide.  1 yard package
 
This is my favorite 'stitch through' elastic. While you may well have 'left-overs' of this elastic, I feel you can easily 'join' end pieces to make a larger piece, using the 'butting on a scrap of fabric' technique as I teach in the video of how I install this great elastic! - find it at this link: 
https://youtu.be/EhnN74KYuAw