I was just looking into this the other day.... Just Google "tyvek wristbands" and you will find plenty of reasonably priced options. You can order them from office supply companies, but they seemed to be more expensive there.

You can normally purchase them at most any office supply store. Although in past years I have simply gone on Ebay and looked for the # needed at the best price... we ended up with 2,000 bands (the nice ones) one year for under $15!

Need vendor to purchase arm bands for our school festival. It will be the first time we offer them to students to serve as unlimited admission for our carnival games. Thanks.