Having visited Tokyo Japan just 2 years ago, I visited several camera shops.
I highly recommend at least 1 day searching the camera shops in Shinjuku, Tokyo.
MAP CAMERA STORE (
View website here level 3 holds plenty of Pentax gear and was my favorite (luckily I still had the website bookmarked)
What I personally did was search google maps once I was in Tokyo. I spent a week there and found many many Camera stores with most of them containing Pentax gear as well. Some of the smaller stores were 2nd hand only.
Most of those shops sold 2nd hand gear.
For me, there is no better place on the planet for obtaining Pentax equipment.
Hope this helps.