Monochrome modified DSLRs are becoming more common. They seem to be quite good performers and open up narrowband imaging to a wider number of people.
Here is an article about how to modify a DSLR to monochrome.
I read on another CN thread that Nikon D90 and D5100s were easier to modify this way for some reason.
This site refers to Canon 1100D mostly but they offer larger DSLRs already modified as well.
http://www.jtwastronomy.com/tutorials/debayer.html
Greg.