My Ha filter is a Baader one, 7 Nm. Alpine Astro sell them in the States
http://www.alpineastro.com/filters/filters.htm#H-Alpha has a transmission chart too.
I think theres also some dealers in Australia that sell Baader stuff too. Custom Scientific in the States make them as well.
Heres a similarily processed image but without removing the other 2 channels and leaving it red.
Scott