For anyone interested, I found something that looks like it would do the trick but it's very expensive for what it is.
In reality, it's probably just a PIC micro-controller with USB support, bit-banging the PS/2 protocol.
I suspect there are plenty of USB and PS/2 PIC code examples floating about on the net so building a similar contraption should be pretty much a case of cut'n'pate with the existing examples.
http://www.kvm.com.au/store/product.aspx?ProductID=5524&CategoryID=311
This is my first post, but I've been watching this thread from the beginning, but now that things are getting closer I must say....
.... I wan't one.
I'll send a PM & email for you to add me to your list shortly.
I too want the new Minimig. I currently have the soon to be obsolete Minimig 1.1 (with all the options) and its an amazing little machine with a 68000 that runs like an 030

Anyway, the device you linked too looks a lot like this device I purchased to put my Minimig on my 4-port KVM which is USB only. I'm coding an application where I need to switch between my PC and Minimig frequently to test.
Anyway, I got this product that looks a lot like the one in your link:
http://www.newegg.com/Product/Product.aspx?Item=N82E16812200976&Tpk=ps22usbIt does work with the keyboard, however the mouse only seems to move up and to the right while randomly pressing the right mouse button. The converter is a partial success because two mice is way better than two keyboards and it does cause my KVM to see a computer on that port. Otherwise the KVM would just bypass that port.
The converter works (with the mouse) on my Amiga 1200 with the COCOLINO PS2 mouse adapter.
Oh, also, I originally intended the converter to let me use the more modern 2.4 GHZ wireless mice with my 1200. It does not seem to work with any wireless USB mice. I ended up tracking down a NOS Logitech 2.4 GHZ mouse with backwards compatibility with PS2.
good luck

nate