Amazon has Scrubbing Bubbles Fresh Gel Toilet Bowl Cleaning Stamps (6 Stamps) for $2.63 when you ‘clip’ the $0.50 coupon located on the product page and checkout via Subscribe & Save. Shipping is free w/ Prime or on orders of $25 or more.
Note: Coupons are typically limited to one per account. You may cancel Subscribe & Save any time after your order ship