There's two sets of them (you get half of the of the dr1 cast in each) and they're both on Amazon.

Here is the link to the first set, which has Leon, Yasuhiro, Makoto, Sayaka, Aoi, Sakura, Chihiro, Mukuro, and Monokuma. Apparently this one is out of stock on Amazon at the moment, but I'd imagine they're sold elsewhere too.

Here is a link to the second set, which has Kyoko, Byakuya, Celeste, Kiyotaka, Mondo, Toko, and Junko. This one is actually in stock on Amazon.