"E" is an abbreviation for electronic, it was very popular in the 90's before the whole "I" fad. It can still be spotted today lurking next to mail.
This project describes the process of building a bola that uses LEDs and batteries as the weights, and a short length of cord as the cord.
Step 1: Materials
Nine 10mm LEDs - Use whatever colors you like. I decided to use a single color for each section of cord.
Nine batteries - Standard 3v CR 2032 Throwie variety
Seven feet of cord - It should be strong, thin, and flexible.
Step 2: Illuminate the LEDs
Attach the LED to the battery with a small piece of duct tape. Each LED / battery combo will undergo a ton of abuse so make sure that they are connected very securely.
To test: Violently throw the illuminated LEDs at walls and other hard surfaces to see if they flicker at all. If they do, reconnect the LEDs to the batteries, and try again.