These things strike my mind. Don't know if it works fine or not:
1) Collect the details required in your web application and send it to Pega via some web-service connectors like REST or SOAP. And at Pega end, configure a service activity that creates an operator with the received details.
2) Some thing like DWA, you can tryout where the link will take you to an assignment and you can collect info, run activity to create operator.
3) See if IAC can fit here. IAC helps integrating pega in other third party websites.