I just tried using a product called "Dissolvo Paper" as a toner transfer paper. Seems to work well.
Posted a photo of my first try in the photo section in the album Dissolvo Paper Experiment .
Printed just like regular paper, transferred with a GBC laminator and rinsed the board under the faucet for about 5 seconds. Paper completely dissolved! This paper has been around about 30+ years and is used in the welding industry. I came across it while working with a technician who was welding up some cryo lines in the lab at work. You can get this paper at magic shops or novelty shops on line. Here are some links. Give it a try.
http://madhattermagicshop.com/magicshop/product_info.php?products_id=6614http://www.kleargear.com/1815.htmlProduct Home page
http://www.dissolvo.com/