It seems that Baader is now another option for us when it comes to narrowband imaging filters. It is my understanding that they have an h-alpha (7 nm), S-II (8 nm) and O-III (8 nm) which are also (!) parfocal to the SBIG filters.
The icing on the cake is the supposed pricing which seems to be extremely attractive and competitive.
I am still looking for further (concrete) details from a couple of friends who supposedly have them.
  