Reached out to this company, who claims to make Silicon protective lenses with IR capabilities designed as a germanium substitute... will post their response once received...
In that case, I might be toast... the window was broken when I purchased the car nearly 2 years ago and water has obviously been infiltrating since (and prior)... thanks!
This is an extremely helpful thread, as I've been trying to find a replacement germanium window for my NVA camera. I've reached out to FLIR to ask a) if they'd be willing to sell / send me a replacement window, or b) provide specifications on the window / to confirm 33 mm dia, 4 mm thickness...