Customers are welcome to bring their own domain names with them over to Polyphony. This is a less ideal solution as it means more work for you, but we support it fully!
We currently recommend Google Domains https://domains.google.com as it is incredibly easy to use, and google accounts are something most of us have anyways.
Once you have your domain name (Congrats!), please follow the instructions for setting up your DNS settings found here.