How to get more current from 555 timer?
An emitter follower will have a voltage in the emitter about 0.6v lower than the voltage at the base. It will work if you don't have a problem with the reduced voltage level.
Note that a 555 with 5v supply can have an output as low as 3v depending on the output current.

The alternative is to use a transistor or mosfet as a low side switch (switching the ground side of the load)







simulate this circuit &ndash; Schematic created using CircuitLab

The mosfet will be a better solution (more efficient) because it has a lower voltage drop across it (drain-source), and it doesn't need a constant current in the gate (for static operation) as the transistor does.
Just select a logic level Nmosfet so that it can turn fully on with low resistance