David at Khromagery
http://khromagery.com.au/index.html does filter mods to EOS digitals. He'll put in a Baader, R72, or clear filter or a few others.
I had my 30D done with a clear filter, so then it was sensitive to UV, visible and IR. The sensitivity to H-alpha went up by about x5. Pity someone pinched my camera...
He won't do a 400D as he said they are too hard to do. He was going to have a go at a 40D this week to see what they are like.