Don't know if anyone else has dealt with this fellow on ebay, but I picked up a couple and have to say they're quite nice and easy to assemble.
Even works with USB to PS2 adapters. At least the USB Micro$oft mouse I have worked.
Seller goes by the handle of kevmeister2003.
If you know which end of a soldering iron to hold, this is a pretty easy project.
Good price too.
Only thing I could ding it for is not being enclosed!
http://www.ebay.com/itm/111172915508
Can't recommend Kevmeister enough.... I have that adapter, and the mk1 version, which came with an enclosure.
you could always mod the mk2 to be more like the mk1, by removing the ps/2 connector and the 9 pin, and soldering leaded versions on.. then the whole thing could be easily enclosed in a small box or length of tube (like the barrel of a chunky pen perhaps) and end caps made to fit.
I also have a CD32 arcade stick interface board and one of his Amipad boards (fully CD32 compatible - it uses the same chips), which I modded into a PSX controller - I have a thread about it here:
http://www.amiga.org/forums/showthread.php?t=66063
