The CDI is the ignition control module, black box, on the left side of the scooter. It has two plugs, the TRICS plug (3 wire) and CDI plug (5 wire). The youtube video below depicts a chinese made substitute known as a "New Racing CDI-TZR50." This manufacture makes a number of similarly labeled cdi's. The plug and play one for the Chetak is the one with the 5 pin connector.
Video Credit: CDI_Compare.mp4 posted to Youtube by RufusSwan
Video Credit: CDI_Compare.mp4 posted to Youtube by RufusSwan