ideas to isolate Java Application WEB in vps to only people that are connected by the LAN [closed]

I am developing a Java web application inside a VPS host.
The application will be accessible from the internet.
However, there is a specific part of the application that I only want to be accessible from the office LAN.
I thought filtering by public IP would be the best approach, but I am not sure if my company has a static public IP.
Could you suggest some alternatives?
Thanks and regards.