Make a PDB unreachable by stopping the listener

I have an Oracle 21.3.0.0 Single Instance CDB with several PDBs and a listener that listens on the standard port 1521. When setting it up, the PDBs automatically registered with this listener.
I would like to interrupt remote access to individual PDBs by stopping the listener, but these PDBs should continue to run.
The method of using different PDB-specific services does not work because I do not have the srvctl tool available (no RAC, no Oracle restart) and internal services cannot be stopped with DBMS_SERVICE.
I was unable to create several listeners with static entries. The PDBs always remain registered and can be reached remotely. I also want to avoid using different ports.