This is a type of cracker also made from glutinous rice (mochi rice). Originally, making these crackers was a way to use the large mochi rice cakes traditionally prepared for New Year's celebrations and set on an altar as an offering to the gods. After sitting out for several days, these barbell weight-sized "rice cakes" hardened stiff. It was the custom to split open the mochi on the 11th day of the new year, but considered bad luck to use a sword (so as not to "cut off" the blessings of the celebratory time). Instead, people used their bare hands or a large wooden mallet, and the mochi would splinter into chips and slivers. The name "kakimochi" comes from this "splintering" action ("kakiwari" in Japanese). In time, this snack was made year-round. The kakimochi sold today is prepared by machine and comes in many different varieties.
Kaki-mochi - also known as Arare(rice crackers) - there are many categories - coming from Hii I'm more used to the savory variety, whereas there are sweet varieties as well. A good place to start would be at a Japanese Grocery - for the true Japanese types. Nijiya or Mitsuwa Marketplace - or even one of those in Sawtelle might be a nice place to start. As for myself, we go to one of the locations of Marukai which is a membership market either in Gardenia or West Covina for Japanese and stuff from Hii (we still drive up once a month, though we've relocated to SD).