Testing SP-Initiated Saml 2.0 SSO: is there a IDP that supports dynamic ACS URL?

I'm currently trying to setup tests to test my application's SP-initiated SSO. This test will be run in different environments, and especially in kubernetes as well, where the recipient/destination URL will be dynamic and different (ie: http://localhost:5000/sso, https://k8s-server-1.com/sso, https://k8s-server-2.com/sso, etc.)

I've looked into free developer accounts with OKTA and OneLogin, and it seems neither supports dynamic ACS URLs. Short of investing time writing a mock SAML IDP of some sort, is there any other resources I can use to test my SP-initiated SSO flow?