I use rubber bands of appropriate size, and have even successfully used a hair band (strong elastic, fabric cover for good grip). My Yamaha CDC is a decade+ old, and I still use it constantly as my primary source (love the level control on the remote).
That said, an official source for proper replacements is nice to know. Likewise, since I have long since discarded my original band (CDC-765), could someone please post the measurements in case I decide to splurge on a new one? Thanks.