RDS/Postgres logs to S3

Hello,

I am looking for an automated way to ship/stream RDS logs 'Postgresql' to S3 to be picked up by another lambda function in order to ship the file to elastic cluster running on EC2.

I published the logs to CloudWatch logs but the only way to send it to S3 is by manually selecting the bucket and the date range. There is option to use CloudWatch Logs Subscription Filters to stream the logs to S3. However, we are looking for something more simpler and cheaper.

Any thoughts?