CD 4047 is the low power Monostable / Astable Multivibrator that requires only an external capacitor and a resistor to give the output pulses.
I was putzing with a project where I wanted to retrigger a 555 monostable. Searches almost invariable came up with " are not retriggable".
An OR gate with one input fed by pin 3 of the 555 should do it, xisf.org discard the 555 and use a non- retriggerable monostable (e.g.:).