You have GOT to check out this thread on a pro photography forum.
http://www.fredmiranda.com/forum/topic/64826/0
Basically, it involves using a simple coffee filter over your lens, pointing at your subject and metering your custom white balance.
I'd be willing to bet this will work for any digital camera.
Make sure you check out the sample pics. I'll try this out on a reef tank and upload some results.
BTW, "expodisc" mentioned costs about $120 and apparently is 5% more effective than 3 stacked coffee filters.
T