Another alternative is to get a flatbed that does negatives such as the Epson 700 or the Microtek i900. I have no personal experience with either of the two listed below.
I intend to use it predominantly for prints and occasionally for negatives. I rarely do medical imaging anymore (where I would want/need the Nikon. Also when I do these types of slides, oftentimes, they are odd-sized.)
I SERIOUSLY looked at the Microtek i900.
$469
I had a Microtek scanner a few years ago, and I really liked the interface, the quality, and they usually run a little less than Epson. Also, the longer "legal sized" bed is nice. I purchased the Epson out of habit.
Note that The Coolscans are dedicated film scanners and do not scan prints. The Epson and the Microtek do both film and prints.