Amazon offers the Krud Kutter Clear House Wash 1-Gallon Bottle
for $22.29. Clip the $3.75 off coupon to cut the price to $18.54
. Plus, Prime members bag free shipping
. (Non-members can spend $35 or more to bag free shipping; otherwise, shipping adds $11.70.) That's the lowest total price we could find by $10, outside of the mention below. It contains no bleach or ammonia and purports to remove dirt, mold, and algae stains as well as gray weathering on wood, chalking, and oxidation.
A close price: Zoro via Walmart
offers it for $14.94 plus $5 for shipping.