switches - Can I achieve a one shot button without a 555?

I have a complex circuit, but my problem only relates to one small part.

I have a relay, which is energised by pulling the low side low using an NPN. I would like a pushbutton to operate the transistor (and therefore the relay) for a time (500ms ish) then deactivate it and wait for the next push (ignoring the button if held). I understand how I can achieve this using timers (or a MCU), but I was hoping there might be a more simple and compact solution...

The image shows a simplified schematic of the starting point...