Looking for AIS data

Hello!

I'm new to geospatial data topic and i am looking for a resource that can help me collect vessels data from AIS.

I'm currently using AISstream.io, but I'm noticing that I'm not getting data from some vessels via MMSI searches, and I was wondering if this was normal or a problem with my Python script. I'm therefore wondering if you could help me to finse a platform that allows me to acquire this data for free or at a low price!