One of the reasons that you don't see many good options for this is because the place where the industry has decided that this should go, when hosting like you want, is on the app itself because of the performance and latency aspects of it. So tools tend to be like this one...
https://shieldon.io/en
And they tend to be platform specific to do a good job. This is something your developers would be doing, not IT, generally. Sure IT can buy third party hosted solutions or hardware, but software is going to be rare because it's an additional reverse proxy that hurts app performance.
So any app big enough to need this is generally happy to pay for Amazon or CloudFlare because the cost is nominal (less than having your own IT research and set it up.) And those that want to host themselves do so closer to the app.