Someone may be interested in this:
Cokin #40 diffraction filter (clear aperture 55mm, 240 lines/mm).
Way cheaper than Star Analyser !!!
http://cgi.ebay.com.au/ws/eBayISAPI....m=130315277127
The efficiency for the first order spectra is not great though, but enough (i guess) for the first stage of this project.
http://www.astrosurf.org/buil/us/spe1/spectro22.htm
I have just obtained this filter for $25 (together with postage, from another vendor on ebay), and it is bran new :-)