Pull and Go Motors

The pull and go toy motors themselves do not illustrate Newton's Third Law ("For every action there is an equal and opposite reaction").

What those motors do is when you pull back you are coiling up a spring (storing potential energy) and when you let go the potential energy is converted into the kinetic energy of the moving toy vehicle.

If you are looking for a toy that demonstrates the Third Law, why not get a model rocket? A rocket is the ultimate Third Law example - the mass ejected out the rear at great velocity equals the forward momentum imparted to the rocket vehicle. You can spice it up by noting that as the fuel is burned, the rocket mass decreases and that means every incremental amount of fuel burned is propelling less and less mass forward, and since it is momentum that is conserved (momentum equaling the product of mass by velocity) less mass means higher velocity, so that the rocket continually accelerates even though the amount of fuel burned per unit time is constant.

If you don't want to go to all the trouble of a solid propellant rocket, you can always opt for the very inexpensive devices that work off air pressure. They don't go as high, and you can demonstrate them practically anywhere - outdoors - not in the classroom.