Redirection Wildcard issues

Hey all.

Just switched over to WordPress last week, set up all our 301s in redirection.me.

One surprise issue:
We have THOUSANDS of users using our SaaS platform that have their own websites at a URL we generate, like:

https://www.ourproduct.com/business/71823

All those links are now dead and support tickets are pouring in. We need to redirect to:

https://app.ourproduct.com/business/71823

Our WP developer says that wildcard redirects aren’t possible, so we are trying to figure out if we are stuck. Any suggestions?

Thanks.