Solution:

It is possible to use Client and Server Authentication Certificates to restrict the access to the Inventory Beacon.  Microsoft IIS has a Security feature called IIS Client Certificate Mapping Authentication.  This feature will enable the option to require SSL and Client Certificate before allowing incoming connection.  This means that only devices that have a copy of the Client Certificate can connect.

The attached document contains further details and instructions around configuring Microsoft IIS and the certificate export and deployment process. 

Additional information can be found in the Flexera Online documentation:

https://docs.flexera.com/fnms/EN/GatherFNInv/index.html#SysRef/FlexNetInventoryAgent/tasks/Common-ClientCerts.html

https://docs.flexera.com/fnms/EN/WebHelp/index.html#tasks/ConfigureMutualTLS.html