Latex bands are the best to prevent against breakage too. That is what most people (including myself) use of the back of bows for topknots. They stay best when they are smaller...you only have to wrap them around 4 times or so to make them stay. You can use barettes and stuff too. We used stuff from the baby section of Target on Linus until his hair got a little longer and he could tolerate daily grooming!
