How to find an event registration invoice better?

From the documentation there: Find the invoice

The recommended query is a bit vague as shown:

https://{{URL}}/api/Invoice?BillToParty.PartyId=21095&InvoiceDate=2019-05-29T00:00:00

For example, what if the user has multiple invoice on the same date?
Is there a better (sure) way to achieve that?

When registering for an event, we have this information:

AdditionalAttributes > AssociatedInvoiceId > 99.00
From my understanding that is an order number.
How do we retrieve the related invoice record from that value using this endpoint:
Returns an InvoiceSummary by id

In other words, how to get the InvoiceId (Invoice) value from that AssociatedInvoiceId (Event Registration) value?

Please help.