The on/off ratio (lambda) tester can be purchased from the following link:
http://www.technictool.com/m0039%20m126-0521.htm
The FAULT CODE COUNTER (124-1921) can be had by making one yourself or buying one from this link:
http://www.baumtools.com/english/specialtools.cfm?CN=3
Also read Steve's article in the DIY section.