a Tiffen yellow #12 as barrier filter is indeed what you need.
Somebody also recommended me a #15 Wratten filter as an alternative.
However, there is a difference in the images you obtain with such glass filters and with plexiglas filters, e.g. those sold by http://www.nightsea....arrier-filters/
the former produce duller images which mainly only show reds and greens, whereas the latter produce brighter and more colorful images,
apparently because they "leak" a very tiny little bit of blue light.
The video mentioned above (http://picasaweb.goo...441065907391042) was made with such a glass filter.
See the difference with a plexiglas barrier filter in this video: https://picasaweb.go...504863416618418