I have some on my site - both the "ouchless" elastic ones you would use with a bow and the covered elastic ones similar to the kind I use for my hair. The covered ones are my favorite for every day. They stay in well but when they do come out they do not rip the hair out at all, plus they look cute without a bow.
If you need like 1000's of them, try ebay. I have seen the ones for braids on there. Just be careful - the kind they sell at Sally's for hair braiding are the rubbery kind that rip hair. Fine for the end of a braid but not a topknot. I've only seen the ouchless kind in smaller quantities like 75 there.