Amazon with zhoukoukanglingshangmao has the 8-Pack Generic Betterchoi Oral-B Sensitive Gum Care Replacement Brush Heads (Soft Bristle) for $5.50 with free shipping on $25+ or with Prime.

• 8-Pack Generic Oral-B Active Charcoal Heads for $6.25 w/ coupon
• 4-Pack Generic Oral-B Double Clean Heads for $6.85
  
• 8-Pack Generic Sonicare Heads for $13 w/ coupon and S&S
  
• 6-Pack Generic Sonicare E-Series Sensitive Heads for $16 w/ S&S
  
• 6-Pack Generic Sonicare E-Series Heads for $18 w/ S&S