You could use a
Baader T-ring/Nosepiece combo for maximum flexibility. It has a 2" filter cell within the "T-ring" housing. Actually, it's not just a T-ring as it also can do M48 thread adaptation (e.g. for a Skywatcher 0.85x focal reducer). That lets you use standard 2" filters in any situation (AFAICS). I just bought one of these, but it's still in the post.
On a related topic, Baader also make a
DSLR lens adapter for 2" filters for the front of the lens - I haven't really looked in to this one, but at first glance, it looks alright, assuming you want to use regular lenses for astrophotography at some point.