On Amazon where you can now get this
Kaboom Scrub Free! Toilet Bowl Cleaner System + 2 Refills for just $6.75 shipped or less after you clip the available digital coupon!

The Kaboom toilet cleaning system easily attaches out of sight inside your toilet tank and injects OxiClean stain fighters into the toilet bowl with every flush, keeping it clean, even under the rim, for up to three months per pouch. Since this set comes with two pouches, you’ll be all set for 6 months!