Every so often I have an idea that makes me feel like a genius! I'm sure you all know the feeling :)
For sets of rubber bands (these are approximately 250) you can use these large skirt/kilt pins from dritz.
larger knitting stitch holders. These come in all sorts of sizes-- I'm not quite sure where I got this glittery one. Be warned that these are easy enough for my kids to open; but the ends are not sharp.
And if you really want to make sure your kids can't get into them-- try diaper pins. I have a hard time opening them myself!
I hope you all find this useful! It's such a simple trick that makes me feel on top of the world each time I do my girl's hair.