For aquarium related shopping, check out any of these stores; I am not sure where you are staying in Tokyo, but they have a maps too...
http://www.adana.co.jp/jp/shop/pref.php?p=13
They all sell ADA equipment to some degree or another. I particularly liked Penguin Village, Pau Pau Aquarium Garden and Aqua Forest.
You may or may not find people that speak English. I speak Japanese, so it wasn't a problem...:smile:
It is too bad it is difficult to bring back livestock/plants/electrical equipment (North America is 110/120V at 60 Hz, in Japan it is 100/110V at either 60 Hz or 50 Hz, depending on Kanto/Kansai region, respectively).
The cheapest way to go from Tokyo to Osaka is by night bus (2300 yen!), but with luggage it is a hassle. Taking local trains is out of the question (takes maybe 6-8 hours?), so your options are pretty limited (shinkansen, airplane, etc)
Here is a list of things to do, just off the top of my head, in no particular order.
Tokyo:
Akihabara (Electronics, anime)
Kappabashi-dori (Kitchen town, they have kitchen gadgets, the plastic food samples that you will inevitably see in restaurant display windows)
Ueno Park
Ueno Zoo
Shinjuku (the area in general; Kabuki-cho (red-light/entertainment district))
Shibuya scramble crossing, Hachiko statue, Shibuya 109 (upscale shopping mall)
Harajuku (Take[censored][censored][censored][censored]a dori, Omotesando dori; pop fashion and high fashion, respectively)
Meiji shrine
Yoyogi Park
Imperial Palace/Gardens
Tokyo Tower
Tokyo Skytree
Tokyo Metropolitan buildings (you can go to the 50th floor to get a view of the cityscape for free)
Roppongi (clubbing, night life)
Tokyo Disney Land
Osaka:
Namba (shopping, Glico man)
Nipponbashi (electronics, anime)
Osaka Castle/surrounding park
Osaka Kaiyuukan (aquarium)
Universal Studios Japan
Kyoto:
Kiyomizu shrine
Kinkaku-ji (Golden Pavillion)
Ginkaku-ji (temple)
Fushimi-inari (temple)
Ryoan-ji (temple)
Arashiyama (park)
Maruyama Park
Kawaramachi (shopping)
Nijo Castle
Heian shrine
Gion (shopping)
Shimogamo and Kamigamo shrine
Kyoto Imperial Palace
Uji (Byodo-in; temple (the one on the back of the 10 yen coin))
Toji temple
Kitanotenmangu shrine
Hirano shrine
From Osaka, you can make a day trip to Kobe, Himeji (unfortunately the castle is under construction), and Nara (Todaiji temple, Nara Park).
If there's anything in particular you're interested in, feel free to ask.