Step 1: Materials & tools
light switch (thicker ones work better)
wire coat hanger (thicker/stiffer ones work better for this, too)
wooden dowel or bead ~ 1/2" diameter
hot glue gun
Step 2: Make the push-pull toggle
Step 3: Prepare the switch
Remove the light switch plate cover thingy. Remove the light switch. Disconnect the wires, but remember where they go before you do.
Drill a hole in the switch that is slightly larger than the diameter of the coat hanger wire, just like the bead. You can do it either top-to-bottom or side-to-side. I've done both, and side-to-side worked a little better for me.
Reconnect the wires to the same points. Reinstall the light switch. Replace the light switch plate cover thingy.
You may now turn the circuit back on.