hi there!
I'm now into my 2nd year of searching too, for pass through light pointer knob.
i wanted for my m-audio xponent that has build in illuminated pots as shown: http://farm3.static.flickr.com/2062/2039075171_fc5977d7cc_o.jpg
here is a website that sells illuminated pots: http://www.cliffuk.co.uk/products/encoders/index.htm
but i didn't find a nice soft touch 6mm "D" type with mark/line/point knob for me yet :/
i tried some diy knobs but i am not satisfied yet. If i make something good i'll tell you.