I'd have to recommend Akihabara too as that's the place where you're most likely to find gadgets destined for export.

My concern would be your finding this device with all the necessary translated (into English) documents, software and adaptors.

The larger shops in Akihabara have whole departments (usually on the top floor) of goods aimed at foreigners. This is where I'd start looking. One alternative is to do what my husband has always done which is shop around, find what you think you want, then go onto the internet to find the specifications and manuals in English before deciding to actually buy it - but then he tends to get professional AV equipment which is more widely distributed worldwide than most of the Japanese 'electronica' (and I don't mean a music style here!!!)