Sphagnum moss is pretty easy to grow. Temps above 70 degrees, a couple hours of light, some moist LFS, high humidity and you have automatic live sphagnum.
You could trade for some in the TradingPost Forum, maybe a nice forum member would give/trade you some. Or, you could grow your own. Buy yourself a bag of LFS from Lowes/HomeDepot, stick it in a pot/container of some sort and cover the top with SaranWrap. In a few months, you should see starts of green growth. It may take a while to get going, but eventually, you'll have tons!
SF