There is no workaround for resources that are not supported for subscription moves. These resources cannot move and you cannot delete and recreate public IP address and expect or request to get the same address.
With careful planning you can create new public IP address resources in advance on the CSP subscription and update your systems and DNS records to the new IP address at a time that will be least disruptive to you.
The only alternative is to leave these resources on the current subscription and use two subscriptions - CSP and Open.