I'm thinking you must mean shade cloth to protect your orchids from the direct sun?
The best type that will last the longest and is available in different densities is called Aluminet. It's available from Amazon and Home Depot, but you won't have the choices of size or density from there, so it's better to look at somewhere like this:
http://www.shadeclothstore.com...
You will first have to figure out what density - from 30% to 60% or more - you will need. It depends upon what kind of orchids you are growing, as well as how strong your sun is. Eg. Hawaii, most of the Southern tier states in the US and also high altitude places with clean air (no pollution) have very strong sun. California, because of their air pollution, generally doesn't have quite as strong sun.
Here in FL, and because I am mostly growing orchids that thrive in high light, I have a 30% Aluminet tarp that I put on the west side of my pool enclosure for the sunniest months, April to June and Sept. to Nov. In the middle of summer it clouds over in the afternoons most days here so I remove it then.
