Bic Camera is famous for being expensive, but making up for it with their card program (which does little for visitors to the country.) Sofmap is easy to find, and on the higher end for pricing. The place where my contact their got mine was from a store called "Naniwadenki" - which is a discount store. The branch he went to was in Osaka, but I'm sure there are others - We ended up paying ~43000 a month ago.
Someone else mentioned that they found one for ~40000 in Akihabara, but didn't say from where.