[Suzu]

I don't remember all the shop's names, but if you walk the main street (from Akihabara station to Suehirocho station), there's plenty of shops that offer toku merch. You might wanna go inside though because they mostly keep toku stuff on the upper floors and you mostly see anime merch in the window. Some of them do have signs with toku images on certain occasions, so that's always something to look for. Also, there is one smaller shop with older toku merch that also has some stuff on display from the outside, but it's like really, really small.
The bigger electronic shops also tend to have merch in the upper floors, especially the one next to the Mister Donut (I think that was Yodabashi camera), but their offer shrunk quite significantly over the last year.

I generelly recommend to take one day or half a day just for strolling around looking for shops that offer what you want.