They're cheap and flexible, they come in many colors, and you can get them anywhere. They're the spiral wristband keychains! They are unually in the office supplies section of department stores. Cut them into loops of 1.5 spirals each. Super easy to put on, and they flex a lot more than the spiral bands for chickens.
I also use an embossing labeler to make numbered bands. It's that tool with the big wheel on top, that you turn to the number/letter you want, pull the trigger, and Ca-Chunk! I always start off with two blank spaces bacause the last part has a pull tab to help with peeling off the backing. Peel it off just a little, and cut the backing. Wrap it around the leg, and stick it to the part with the blank spaces. These labels come in many colors, you can write whatever you want on them, and they are permanant. Handy, but you do need to replace them on chicks as they grow, unless you leave them loose enough to allow for growth. Plus, they are accepted in the show ring.
My favorite legbands are chunky plastic snap-on ones from Foys Pigeon Supply. You can mix and match colors - I don't get the numbered bands, but these are thick enough that I can write numbers (or letters, for whatever weird code I'm using to identify them) on with Sharpie. I just ordered 150 of them in three different sizes and 6 different colors for less than $15.
I don't like the thin plastic spirals - too hard to get on and off.