i got mine from zadro (
http://www.zadroinc.com/). they have all different types and seem to be the fogless mirror experts. it worked well until it, well, started fogging up. there's this little moistwipe thing they give you with it that fixes that problem. i've never seen a 'cheap' (i.e. target/wal-mart) fogless mirror that actually works. i have heard that shaving cream thing, though--gonna have to try it.
i agree with the other posters, though--i shave in the shower by feel, not by the mirror. generally you can only see a certain amount of your head, and once you know what you're doing, well--you know what you're doing. you know?