I have ordered a Garmin 705 that should solve all my problems. Looking forward to it arriving soon.
Last Sunday I rode back from Tamagawa and thought I'd need a map. I had a map (book) of Tokyo and pulled it out of my back pack twice just to check I was on the right path. Both times I was and didn't really need the map after all.
At least with any kind of map you have peace of mind.
I've sometimes wanted to photo copy a map route and put it in my back pocket but usually just memorize the route and pray. Getting lost is sometimes the best part of a ride. You go somewhere you would never have gone and sometimes find something interesting in the process.
Maps I've bought and rarely used.
TOKYO Metropolitan Atlas. (took it last weekend).
http://www.amazon.com/Tokyo-Metropolitan-Atlas/dp/4398201033/ref=sr_1_1?ie=UTF8&s=books&qid=1217995539&sr=8-1
Touring Mapple (All in Japanese but has nice motor cycle routes high lighted).
Road Atlas Japan. (Good for dreaming of those long rides when I have retired)
And a whole lot of others I had used in the past in my car before I got a car navi.
If you can memorize a few of the major roads, major train lines and major rivers then you can always find your way home... just keep riding till you bump into one.
Map my ride is good but I have only used it to plot courses I've already ridden just to see where I went.
http://www.mapmyride.com
My Sunday ride...
http://www.mapmyride.com/ride/japan/futako-shinchi/44256033
With the ride last week I started from a bbq on the Tamagawa and just headed towards Tokyo Bay. When I saw Kawasaki I decided that's enough river riding, I'll head into central Tokyo and see what happens. Got on route 1 which was lucky as it kind of has a cycling lane... nice ride past Tokyo Tower up to the palace past Tokyo eki (close enough) then bumped into good old route 6. Easy. Didn't need a map at all.
Omiya is near Arakawa so you can always use that as your runway home. I use the Edo river as mine.
Maps are good to peruse over for hours and the more you do that the less you need them.