[Backtobasics]

Here is what I would do:
Buy the replacement converter, and have a muffler shop weld 2 flanges onto the end of the converter. Have them also weld 2 flanges into the exhaust. Have them also weld up a straight pipe with the 2 flanges. I would keep the converter for next year when you have to have the test, and bolt it in place of the straight pipe that you run daily.

While I acknowledge that a converter does the job of cleaning the exhaust for better air, I also take into account that the car is already burning oil. The converter is not going to fix that. For me, my comfort would come in knowing I am trying to be as efficient as possible, and while the car is putting out emissions, having a converter on there that is contaminated and not able to do it's job, is not really a benefit to the equation, and more of a hindrence, as it impedes exhaust flow, especially as it get more and more clogged with oil residue. I'd buy one more converter, run a straight pipe, and put the converter on before the test so it passes.