Jon, there are usually a few on Ebay. The trick on later model vehicles is getting a gas sample upstream of the catalytic converter. It usually requires that a bung be welded into the exhaust pipe ahead of the converter, and plugged when not in use. Then you'll need a pretty good length of heat-resistant flex tubing because of the temperature of the exhaust gas. I used my 4 gas machine during dyno runs on racing engines- - - -sampling the header collector exit gases. Quite an education!
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!