There is/was a post from way back with a DIY solution that uses rubber tubing etc. It is a bit crude, but I tried it and it works. I think that it was on this site (but I may be wrong). I am also pretty sure that when I did it, I followed a video on youtube where someone did a step by step guide, but this was a while ago. Depending on your climate and the amount of condensation, you may have to use a hair drier on the lens for 30 minutes to an hour to dry the inside completely first. I remember my next door neighbor asking me why I was drying the car with a hairdrier – there is no good answer to that one. If I find the post I will come back with the link.