The parts are very common and not expensive to buy.
You will need -
2 x 2N3904 NPN Transistors.
2 x LED's , standard 5mm types.
2 x 100uF 16V Electrolytic Capacitors.
2 x 470 Ohm Resistors.
2 x 10K Ohm Resistors.
1 x 9V Battery.
None of these parts or values are critical , so
experiment or use what you have on hand.
The only critical thing to remember with this
circuit is that it has many parts that can only go
in one way around.
So check your polarities and your transistor pin
outs to be sure its right.
Here is the video of the Flip-Flop that I made , but
will it work ?
Watch it and find out :-)