Hi, I’m Wonkie, and most people know me on the Topre discord as BaitedB8, and I finally found the replacement cable for the HHKB Pro Hybrid (and most likely the Pro Classic boards) for $42.
Some backstory to this search-- I was mindlessly modding my Heavy Grail, and one of the blue coaxial wires snagged onto one of the PCB screws, and I had screwed it in, ripping the wire.
My $1000 Heavy Grail suddenly became a paperweight, and I was on the search for another Pro Hybrid to harvest the ribbon cable. I stumbled upon a Geekhack thread in which Hasu identified the cable, and it’s the manufacturer: I-PEX CABLINE-VS 30 pins. However, I-PEX does not sell cables and only sells the connectors to cable manufacturers/companies that would assemble them and not direct customers.
Only thanks to @insolentpotato were I able to find a seller of these VS CABLINE cables,
The first seller was Quadrangle Products, which was quite the process to purchase 1 from.
You would basically need to request a quote, and a sales engineer would send an email asking for the product code, and at the time of purchasing, there are only 7 cables left. The sales engineer would give you a product code, and you would need to go back to the website and fill out a buy order form. Since there was no online checkout service on their website, someone from their sales office would contact you by phone and ask for your CC info, and then they’ll ship out your cable within the next day.
I was also told of another place where you could purchase a CABLINE VS cable on DigiKey, but this cable DOES NOT work.
Anyways fast forward a week, and I finally got the cable from Quadrangle, and it does not look similar to the OEM HHKB Cable, but I plugged it in, and it worked!
TL:DR
the HHKB ribbon cable replacement is the IPEX 20453-030T to IPEX 20453-030T cable,
I have not found a consistent seller of these cables yet, with Quandrangle semi-requiring you to be a part of a company/college/business to purchase one. There is a Chinese vendor of these cables I found, but it has a MOQ of 100, and I have no clue if they work or not