FYI - depends if you want to go further than CP2. I would recommend you do.
I cant remember if usbmon was on the CP2 CD or not, to difficult for me to find in one of many boxes to check but files listed below are the last USB packages from IBM.
usb10162.zip Last IBM Base USB package. This is the same file as usbbasic10162.zip. If you are doing a fresh USB driver install, start with this one. Includes hcimonit.exe, usbd.sys, usbehcd.sys, usbhid.sys, usbohcd.sys, usbuhcd.sys.
usbp10157.zip Last IBM Printer USB package. Includes usbmon.exe, usbprt.pdr, usbprt.sys.
usbs10162.zip Last IBM supplemental USB package. Includes usbcdrom.add, usbmon.EXE, usbmsd.add, usbwarn.EXE.
You will want usb10162.zip (20th Jan 2006) and usbs10162.zip (20th Jan 2006).
Happy to email these to you if you like.