I am having the same challenge. It doesn't even show what each attendee purchased for passes- it just has the transaction total and a list of attendees. It would be best if the response from the finalization of the registration (msevtmgt_FinalizeExternalRegistrationRequest) returned a list of the registration id's that were created, instead of only containing the word "success".
The best workarounds I can come up with are all bad:
1. Don't reconcile payments to registrations.
2. Manual Reconciliation- pass in the attendee info to the payment gateway (we're using PayPal) so that someone can reconcile attendees to payments manually.
3. Email Reconciliation- require emails to be unique, either on the front end or when pulling the Purchase information. Then after registration is complete, pull the registrations by email and match them to the purchase (because of the lack of pass information this would have to be at a summary level based on Correlation ID)
4. Time based reconciliation- pull the most recent registration that matches based on email address and connect them. Hope that two people don't register with the same email at exactly the same time.
Hopefully we can get a real answer.