Probably a very naive question from a (semi-retired) 70 year old Mathematician. I’ve spent all my working life in different IT roles. My main areas went from junior Programmer, Programmer, Analyst Programmer, Systems Analyst, Head of IT etc. I’ve always been on the (Pure) Mathematics/Algorithmic side of the fence, my practical, Network and EE skills are minimal.
So I’ve just received a working TI-95 Procalc. I have a TI-89, 92, Voyage 200 and a couple of different TI-Nspires.
The original cable I believe that would have connected the TI-95 was 10 pin female to 25 pin (centronics?) at the PC end yes? Exactly the same cable was used by the TI-74? They are like Hen’s Teeth to find one? Even if I did I no longer have an older PC with a 25 pin port. A 25 pin to 9 pin serial adaptor won’t work? There was never a working cable that could connect the 10 pin port of the TI-95 to USB?
So here’s the naive question → Given that we’ve always been able to connect 2 identical TI Calculators together with the standard 3.5mm jack cable, I.e. TI-89»TI-89, TI-92»TI-92 etc., would it be possible to connect my TI-95 to either my TI-89,92,200 or Nspire and then use the fact that the 89,92,200 or Nspire CAN connect to a modern PC with an USB port to copy/save/load files back and forth from the PC to the TI-95 by using one of those other calculators almost like a bridge or staging post, especially as I’m highly unlikely to ever get/find an interface cable and I lack the EE skills to build a cable or even understand the schematics?
I also understand that there was also a cable that connected the TI-95/74 to a tape cassette for loading/saving programs to tape. I have the TI-95 and a number of working tape cassette players (even a reel to reel!) but again no interface cable or way to make one.
Can anyone help me please?

Looks like you asked the same question elsewhere, which points me at some helpful resources at least.

That connector is a "dockbus" connection, which a commenter on stack exchange says is documented in the TI-74 reference manual, with a copy available on some random site. On the 74 it's "hexbus."

Just some initial notes, I'll probably look into this in more detail when I have an opportunity.

Interestingly enough there appears to be some form of emulator for this calc?

http://www.datamath.org/Calculators.htm#Other

The short answer to your question appears to be that it's infeasible to use another calculator as a bridge, because the expansion bus on the 74 and 95 is much wider than the serial I/O port on the newer calculators- it transfers 4 bits at a time and has additional signals as well.

The simplest way to interface with a PC might be to act like a tape recorder- use the PC's mic and speaker outputs. It seems to just want a nice clean square wave, so it may even be possible to communicate through your computer's audio interface without any special hardware- just connect pins 3 and 6 to the speaker and mic respectively with a common ground, then a little software might do the job.

Datamath has some photos of the official CI-7 cable, which appears to just be an amplifier with some filtering. The parallel port cable is known as a PCIF and I suspect it just does level conversion, with bus translation handled in software. Unfortunately I haven't seen anything that outlines how the bus transactions actually go when talking to a computer, so it's hard to tell how difficult translating that would be.

Edited:
Never mind, found a PCIF schematic. It's level shifting and some latches for control signals. What kinds of signals go across that while in use remains a mystery.