I was thinking that even though it's not visible, the Created From field (or maybe Applied to or Applying) on Amortization JEs will show the originating transaction.
If not, does the join from a transaction search>Amortization schedules not get you what you need?
Due to the join limitations on searches, you may have to start with an Amortization Search and then join from there to both the bill and resulting JEs, but I think one way or another you should be able to get there.