help with these dollfie dream rubber straps?

a while ago i stumbled across these rubber straps/keychains of dd natsuki, moe, and both versions of mariko from akihabara girls, listed on mandarake. they seem official and are in the same chibi style volks uses... googling in english, japanese, and reverse image searching resulted in nothing. :,) the title suggests they were a gacha prize or something?

does anyone know more about these/own one? i'd be super interested to find out if they made ones for all the akihabara girls (akira, alna, etc)!