Frozen Oral B Pro-Health Jr Sensitive Clean Replacement Brush Heads 3-pk Walmart $5 YMMV
Just found a bunch of these Oral B brush heads for $5 each. The look like old Frozen stock but they are for the standard Oral B electric toothbrushes. I usually buy my Sensitive Cleans from Amazon as low as $11 a couple years ago to $15 each. Per Brickseek I see they can come at $3. Good luck!