Here you go, $95 plus post, some soldering required. Add $30 to not solder with the model up

Thier real products look pretty good too, have seen very frew negative remarks for thier products

https://www.14point7.com/products/sigma-lambda-controller-free-2 $45 without the sensor

I don't think using a cut out and short length of tube will work the best. One of the reasons the sensor is meant to be as close to the port as possible is to avoid outside air contamination from the end of the exhaust system

If you're already playing with Arduino style stuff you might get out of it cheaper than that, but at the expense of time and faffing about.