Below is a suggestion based on your ask.
Private ingress controller can be installed which would be available within the Virtual Network only (not accessible for internet or other virtual networks).
Then APIM can be configured to redirect the traffic to this ingress controller basis the hostname, path etc.
However, IP of APIM is not required in ingress controller and moreover the IPs of APIM can keep on changing. So it is not recommended to embedded it in the ingress controller. You can read about private ingress controller here.
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