This circuit was found in a Poptronics of the 90's. The components can be changed to the desired frequency. The power supply must be symmetrical.
Texas Instruments ESD122 Electrostatic Discharge Diodes (ESD) can be ordered from Mouser...
This alternating flashing system uses two-color LEDs. The circuit is from a Radio Electronics...
I found this simple circuit from an English magazine from 1984. The circuit can be easily...