I haven't shot infrared and I'm unfamiliar with the filter designations, especially B&W's nomenclature.(posted 9008 days ago)However, there's a place in Skokie, Illinois called American Science Surplus. They sell all manner of very interesting things, many of which could have/do have photographic applications, including a very large, semi-spherical infrared filter - i.e. it blocks everything BUT infrared. I have though of buying on from time to time but I really haven't mustered the interest.
It is, considering it's size and quality, quite cheap as I recall. I know they are on the web. Thing is, being military surplus, it isn't a conventional screw in glass filter, you'd have to rig some sort of attachment to use it. I believe it's in excess of 3" in diameter.
Hope this helps