Create an Amazon DynamoDB table to maintain all IP address ranges and security groups that need to be updated. Update the DynamoDB table with the new IP address range when the company adds a new partner. Invoke an AWS Lambda function to read new IP address ranges and security groups from the DynamoDB table to update the security groups. Deploy this solution in all accounts.

Create a new prefix list. Add all allowed IP address ranges to the prefix list. Use Amazon EventBridge (Amazon CloudWatch Events) rules to invoke an AWS Lambda function to update security groups whenever a new IP address range is added to the prefix list. Deploy this solution in all accounts.

Create a new prefix list. Add all allowed IP address ranges to the prefix list. Share the prefix list across different accounts by using AWS Resource Access Manager (AWS RAM). Update security groups to use the prefix list instead of the partner IP address range. Update the prefix list with the new IP address range when the company adds a new partner.

Create an Amazon S3 bucket to maintain all IP address ranges and security groups that need to be updated. Update the S3 bucket with the new IP address range when the company adds a new partner. Invoke an AWS Lambda function to read new IP address ranges and security groups from the S3 bucket to update the security groups. Deploy this solution in all accounts.