Well I decided to get creative again, this time I have made a dewshield for both my finderscopes. It is just made out of black card and sticky back plastic to give it some water proofing. I have made the shields just the right length so they can be kept on the finderscope when not in use, and they just slide forward when the time comes.

Dave,
Looks good! I find lining the shield with felt helps fight dew. I came acroos this supplier of adhesive flocking and might give them a try - the price is certainly good.
http://www.abmshop.co.uk/
David