IR is not needed with Gen 2, 3 or 4. In the military we only used it to signal to others when we KNEW there was no one else around with NVG. Other than that, I have never found the need for it.
As for the Gen 1’s out there, you can get the “Ghost Hunter” model that is about the closest to Gen2 as you can get.
IR is for illumination when your NVG’s don’t get enough light to the tubes. Get something wtih a good tube and you don’t need the illumination.