I had the same on the front passenger and drivers doors and it was spoiling an otherwise impeccably quiet drive.
I bought some of this cloth wiring harness tape for another job but wrapped some around the lock plunger and it completely solved the rattle and blends in perfectly.
https://www.ebay.co.uk/itm/WIRING-CA...M/360742292255
It was a bit fiddly thanks to my massive clown hands but it doesn't interfere with their operation at all as the cloth tape is very thin, just don't layer it up - you only need one layer all the way around.