Derek,
A Lambda port is another term for oxygen sensor bung. These can be purchased from most auto suppliers. You can get the sensor, the bung and the close off nut or buy them individually. There are some different sizes, but Bosch is the largest supplier.
Placement is important. No more than 8" from the port for singles. You want to place the sensor where the flow is high and the temperature is high so there is no moisture on the sensor. Moisture will give odd readings. On cars the placement is usually further downstream just past the end of the header in order to measure all of the cylinders.
Flow guys hate these ports because they interupt the flow in the exhaust pipe. It is not unusual for them to thread in an aluminum plug and grind it smooth from the inside to minimize the problem. If you do not have a port, a wand with a sensor can be inserted in the pipe.
The sensors generally plug into a moitor that has a power supply:
https://www.pegasusautoracing.com/group.asp?GroupID=O2SENSOR
David