What is that item of clothing/accessory called that is two clips on the end of an elastic piece, which is clipped to the back of a woman's shirt to make it tighter?

I am looking for the item that consists of two clips that are attached to either end of about a six inch strap of elastic, that’s clipped onto the back of a woman’s shirt to pull it tighter. This might be if the shirt is a little too big, so it would be a hidden way to tighten the shirt.

It’s kind of similar to the thing that is used to clip mittens onto kids’ jackets, so the mittens don’t get lost. However, a mitten clip usually has a cartoon or other picture on one end to make it attractive to the kids, but it would not do on the back of a woman’s shirt!

I see them sometimes in the store and they are good to have. I would gladly order one on the internet if I only knew what it was called.