Now, your "buzzer" and your circuit are completely different.

Before you had a DC beeper and now you need an AC piezo speaker.
Before when P1 and P2 are switched together, the 555 would try to turn on the beeper after a delay time. But a TLC555 is too weak to do it with a 3V battery.

Now the TLC555 makes a tone and the piezo speaker plays the tone, some frequencies at a very low sound level and resonant frequencies a little louder. R3 will stop the TLC555 (3V/150 ohms= 20mA) and is not needed.

 

R3 is just for a simulation of a piezzo buzzer (i.e. R3 is the buzzer actually). TLX555 has Sink: 100-mA typical so 20 mA is without any problem.

 

Your new circuit has no timer. Its piezo speaker plays the tone all the time the circuit is powered.
Then you do not need the circuit, instead power a piezo buzzer (with its oscillator built-in) directly from the battery.

A piezo buzzer (with its oscillator built-in) will be much louder than a piezo speaker because its oscillator automatically operates at its loudest resonant frequency.

With a 15V supply, a TLC555 output low is 50mA to 100mA.
With a 3V supply, the output low of a TLC555 is only 1mA to maybe 3mA.