Need plane-3.8.3 firmware file for Cube Black/PX4v3

Does anyone happen to have a firmware file for a Cube Black/PX4v3, version 3.8.3?

Somehow it is no longer available, neither via https://firmware.ardupilot.org/Plane/ nor with Mission Planner or QGroundControl.

If not, is there any way to access old firmware files, especially 3.8.x?