There is an Ebay store from the GTA that sells Smith IO goggles.
Most of them come with the Ignitor Lens plus an extra lens.
Here are a couple examples:
Ignitor Lens + Sensor Mirror
Ignitor Lens + Green Sol-X
Ignitor Lens + Red Sol-X
Given that they all come with the Ignitor Lens, what is a good 2nd lens that I should look for that would allow me to change between the two to account for the majority of boarding conditions (bright sunny, cloudy, snowing, night, etc)?