Ever tried a Hoya 49mm uv-ir cut filter? For a 2" filter they work out cheap and have full cut off at 700nm and appears it only starts to cut at 680nm. They are way cheaper than baader etc. You can remove from filter via spring circlip and use unmounted... Thoughts?
http://www.hoyafilter.com/hoya/produ...lters/uvircut/