Orchidweb.com has it Supplies - Potting Media - OrchidWeb Pricey, but if you are preparing Neof. falcata for shows, likely not a lot of options. Or do you live near a Bonsai store that might have it?
I go through a lot of sphagnum so I get the large bales from Fred at SVO. It's very good stuff, one mile moss. the best part is that it has tons of long strands for wrapping neos. you just need to sort it out if you need it for that purpose.