You can probably cut the bung peice off a vehicle at a wrecking yard.
Yep, you can salvage one or make a new one from scratch. I've done both:
![](http://inlinethumb57.webshots.com/38392/2598199820042310107S600x600Q85.jpg)
Here's how to make your own O2 sensor bung.
I started with a piece of 3/8 steel and marked the outline with a gasket and drilled and tapped some holes (8mm x 1.25):
![](http://inlinethumb38.webshots.com/15525/2328652750042310107S600x600Q85.jpg)
I used some exhaust studs from the dealer that were left over.
![](http://inlinethumb60.webshots.com/30907/2311004980042310107S600x600Q85.jpg)
Then I started cutting it out with a cutoff wheel on an angle grinder:
![](http://inlinethumb04.webshots.com/13763/2832232260042310107S600x600Q85.jpg)
After using a grinder and beltsander to smooth it out:
![](http://inlinethumb40.webshots.com/29863/2307277930042310107S600x600Q85.jpg)
Now that was one bung, but I need two for my 5VZ. The first one took me about 2-3 hours to make so I decided to try cutting an old one out of my old 3.0 exhaust pipe and using it. That took about 2-3 hours too, counting replacing the old studs and smoothing it out with a grinder and beltsander too.
Here's the two side by side, the one I made from scratch will have to be welded in parallel to the pipe since it's not curved to the shape of the pipe:
![](http://inlinethumb08.webshots.com/8135/2007221190042310107S600x600Q85.jpg)