I have a similar issue with my 4041. I have been attempting to reverse engineer the tape controller with a view to making up a tape emulator based on an SD card. However, due to lack of time and it being a difficult circuit to decipher, I haven’t made much progress on this.
In the interim I have been experimenting using a terminal emulator, via a custom adapter to convert RS232 to the keyboard port logic levels, to enter suitable commands to transfer the console port to the rear panel RS232 port. On this port I connect a PC terminal emulator and can use the PC to edit, upload and save programs. At the moment this is a tedious process as I have to enter the initial commands into the terminal emulator by hand but I have been thinking of programming up a little micro controller to fit inside the LEMO plug and automatically squirt the requisite commands into the keyboard port every time the 4041 is powered up. Again, due to lack of time, I haven’t made any progress on this.
I see from your signature that you are a Kiwi. I am located in Christchurch. Perhaps we could get together and collaborate to make these 4041s usable again.