For Firefox or Tor, just enter about:support in your URL bar in your browser.

Scroll down to the section titled "Add-ons", and grab the ID for BPIP.

Then scroll back to the top section titled "Application Basics" and click the "Open Folder" button beside where it says "Profile Folder". The extensions folder is in there. The BPIP XPI file will have the same name as the ID from the previous step.