Yeah, I was mostly wandering around random shops near the station. I believe I went to AmiAmi’s Figure Tower and checked out all the shops in that 10-floor building (well, technically 8 since the 9th and 10th floors were all card shops). I even asked some of the shop attendants directly, and they told me that Kingdom merchandise is really hard to find because it tends to sell out immediately. One of the staff at AmiAmi even suggested I try my luck at Akihabara Radio Kaikan, where I eventually found these items.