HDPE Shade Cloth is typically used when shade is the primary
requirement and waterproof fabric is not necessary. Shade cloth is
knitted as opposed to woven like most other fabrics. The fabric is
relatively inexpensive and with several manufacturers there are
dozens of colors to choose from. Here are some of the most
reputable manufacturers:

 

http://www.alnetamericas.com/resources/#extrablock
http://www.galecommercial.com/product/commercial-95-340
http://www.monotec.com.au/monotec-370.html
http://www.polyfabusa.com/polytex.html