Unable to find the older version of aws cloud watch agent.

The older version, that I think you are referring to here, is the one prior to the unified agent. This has been deprecated, however you can still manually download the installer here:

https://s3.amazonaws.com/aws-cloudwatch/downloads/latest/awslogs-agent-setup.py

Documentation for the use and installation of the awslogs agent is available here: https://docs.aws.amazon.com/AmazonCloudWatch/latest/logs/UsePreviousCloudWatchLogsAgent.html