Got some unexpected time off... so cleaning the shop.
$65 plus actual shipping.
The hardware, metal spacers, and metal plate that are specific to the C10 are in excellent condition and were used on my '99 -- always garaged. I sold the bike but kept the Givi box, so ordered a mount kit for my replacement bike ('96 BMW R1100RT).
I used my original plastic mount on the BMW. So the only part that could possibly ever wear out -- plastic mount -- has zero miles, it's never been installed on a bike.
Here's a link to the part -- which is no longer available:
https://www.twistedthrottle.com/givi-topcase-rack-kawasaki-concours-gtr1000-zg1000Here's a pic of the actual parts, laid out the same as in the Twisted Throttle link above.