The flashlights in Akihabara are usually cheap imports and its rare to find anything that will not be bettered on cpf, but there is one shop that carries SF though the brand name products are expensive.
There is a great shop in ueno market called malugo, its small but easily has 100-200 products and the price is reasonable for Japan.
Tokyu Hands has a modest flashlight section but they are usually extremely overpriced, expect 2x ~ 4x US prices.
Some of the large electric retailers like BICCAMERA, Kojima, Yamada, can sometimes have unique items as can some of the DIY HomeCenter type shops so if you pass by them, you might want to take a look inside.
Best of luck!
tgwnn