Looking for sealer

I'm looking for a crystal clear finish for exterior wood decorations. A long time ago, I used a product called CARVER TRIPP Liquid Plastic. When you opened the can, it looked crystal clear like water. No yellowing, no milky product. I can no longer find this product so I'm looking for something to replace it. It has to be able to go over Acrylic Paints. Any suggestions would be greatly appreciated.