I just recently started using http://www.tallmenshoes.com/
for height changing shoes. Sucks because I'm 1" shorter than my cosplay partners and I always need to be the crazy tall guy >_< I'm really happy with the shoes I got from here since you couldn't tell that I was wearing them. Additionally I haven't tried the $6 elevator insole, but if they're like the ones that were in my shoes they should be fine. Just be careful that since they're dress shoes, you might pop out of them if you put in too much height.