The store was called Yodobashi camera
Sony's statement on why it was discontinued seems to be this -
"Sony's statement on the BKC50 Bluetooth Keyboard with Tablet Cover Stand
We regret to inform you that we are stopping the global launch of BKC50. The background is that the closing magnet had to be removed as it affected the sleep mode/wake up function of the tablet, which consequently implied a risk that tablet would fall out when carried. This decision is fully aligned within SOMC top management. We are looking into a potential back-up solution and will inform you as soon as we have more clarity about this. We apologies for any inconvenience caused."
They aren't selling it on their site, but a google search will show you can find it on eBay and Amazon.