hp does not sell the TBolt cables as separate items only with the card
however most TBolt cards are based on the intel reference design and have the exact same header pinouts all of the HP TBolt 2/3 cards i have seen are based on the intel reference board but i've obviously not seen them all
this previous posts has picts of the cable ends
the issue arises on the motherboards' most TBolt 3 motherboard headers are 5 pin but can be wired differently
it should not be that hard to use a multimeter on the MB and determine the gnd/power pins leaving only the two data lines which if wrong will not cause damage just swap if wrong this allows you to use a dell or lenovo TBolt cable for example
last check your systems "service manual" for some systems the MB TBolt header pinout is documented
note one pin is missing on the MB 5 pin header used to key the proper insertion