The OP has taken a fair and reasonable approach IMHO. Maintaining a courteous line of communication is the sensible thing to do at this point. If you make it easy for Keysight to achieve their goal quickly and without fuss, then as well as the speed of resolution of their problem which will no doubt be well received by whoever is driving this chase, there is an economic incentive for them to be more generous in providing a replacement product.
All these attitudes of "stuff you" are simply silly. Digging in your heels "on principle" for a situation like this just sounds like somebody being a stubborn old goat for no good reason. It's not as if the equipment was part of grandpa's lab and had irreplaceable sentimental value.
If what is offered to the OP to "make whole" is something they would be happy with, then why be an asshole? Besides, if you do make an enemy of a big corporation that has the resources to pursue with greater intensity, you could find yourself in a world of hurt, especially if there are some national security implications.
Let's see what Keysight's response will be.