This Cable is part of the HP 08555-60077 Service Kit which I have been looking for as a useful accessory for some time, but I have never seen one on eBay. These special cables are available from GLK Instruments, plus there is a Plug-In Extender Assembly HP 11592-60015 between the RF & IF Sections and the HP 141T Display Section, both very expensive though!
July 2018
I was considering making up this cable from spare parts, see HP 8553B Parts and buying a scrap IF Section to obtain the special D-Type Plug and Socket. A quick check on eBay and there was one for sale locally for a bargain price of £20. Serendipity!
The actual connections vary between the Plug-In Sections, see HP 8552B Mating Connections for details. However, all the pins are connected end-to-end in this Cable.