Amazon offers the Philips Sonicare E-Series Replacement Brush Head 3-Pack, model no. HX7023/64, for $29.99. Clip the $4 off coupon on the product page and add it to your cart via "Subscribe & Save" to drop the total price to $24.49. With free shipping, that's the lowest total price we could find by $13. They feature angled necks and "reminder bristles" that fade when in need of replacement.
Note: Be sure to cancel Subscribe & Save after your order ships or you'll be billed for subsequent shipments.