This is a great video on how to make your own LCD viewing Hood...

There are two different versions on his website.. I'd imagine if you
made one from thin plastic sheets it would work too...

YouTube - Canon HV20 HV30 HV40 LCD Hood - Paper Version that Folds Up - Hoodman (http://www.youtube.com/watch?v=VGwos9S6fzA)

Here's the web page to download the templates...

http://www.bitmaster.com.au/fold3d/models.html