|I must give credit to Mary Mulari, the sweatshirt queen, for this tip. I saw her do this on a Nancy Zieman program and have been using it ever since.
Go to the dollar store and buy a packet of fabric coated elastic hair bands. Use these for button loops. They come in all sorts of colors or you can get a pack that is just black. I insert them into the seam, making sure I measure from the stitching line, not the cutting line, and stitch them in back and forth with a 1.5 stitch length.
They stretch wonderfully around your buttons and are minimal work.