What would be an inexpensive non-toxic acrylic sealant I could use to seal my waterfall. The waterfall is made of concrete and grout. I would like to use a product called Shields All, but the shipping cost is as much as the product. And it only seems to be available from one place online. If you have used something with good results please let me know. My search has not gone as well as I'd like. Thank you!