Baby play groups

My son has just turned 5 months old and is becoming more curious and active. Does anyone know if there are any baby play groups for babies around this age so he (and I) can socialise?

Whenever i search on google, only kinderdagverblijf en kinderopvangen show up and we will not be sending him to either as I am a stay at home mom!

Anything suggestions in the Rotterdam and drecht-areas are appreciated. Thank you!!

Edit: it doesn’t have to be English or expat-focused. I speak and understand Dutch, and he is being raised Dutch.