Uni-Fam via Amazon offers the Uni-Fam Replacement Philips Sonicare Toothbrush Head 3-Pack for $12.99. Coupon code "WKYDAMQF" cuts that to $5.20. Plus, Prime members bag free shipping. That's $15 off list and the lowest price we could find. They fit a wide range of Sonicare toothbrushes, listed on the product page.