We have made garters for our family weddings. You can take 2 pieced of ribbon, sew together, and you can also add some pretty lace to one edge. Slide a piece of elastic through it, makeing it the size you need. Sew up the edegs and the opening, and your done.
Laura, I made garters for all my proms and dances and gave it to the guy as a keepsake. They always matched my dresses. The guys always loved them. I kind of wonder now, if they only asked me to get one? lol. I did they same as Michele said above. I would also look for trinkets to sew on the bow.