Amazon offers the 303 Instant Windshield Washer 25-Tablet Pack, model no. 230371, for $9.29. Check out via Subscribe & Save to drop the price to $7.90 and bag free shipping. That's the lowest total price we could find by $4. Each tablet makes one gallon of cleaner and is formulated to purportedly remove bugs, road film, dirt, and grime from windshields.
Note: Be sure to cancel Subscribe & Save after your order ships to avoid being billed for subsequent shipments.