We have to buy it here, but it does last if you keep it out of the sun and mist it now and then. The kind Marcin is talking about, I don't want! Shady, damp places don't work well with most orchids, though I did recently buy a Gongora that has live moss in the basket...
Marcin, I have seen instructions on the internet for growing moss by pouring milk on the wood, rock, whatever, and attaching the moss to it, but where you would get the moss , I don't know, unless you collect it form the wild.