Secure Web Portal As Service

I am on a small team which deploys a variety of web services on AWS for internal use on the team. These services have a public IP and we do our best to secure them, adding a firewall and authentication.

However, we are not security experts, and it is possible that we've missed a configuration setting, or we miss an upgrade to patch some new vulnerability.

We are wondering if it is possible to outsource our web security: something like Secure Web Portal As-a-Service. I'm imagining we could rent an online portal which handles the authentication, and then proxies all users through a static IP, and we add that static IP to a whitelist on our firewall. In this way we could still set up our own web servers, but somebody else could handle the security.

(What I'm not looking for is a guide of how to set up such a thing on our own. The point is to pay experts to do this set up for us!)

Does such a service exist?