LWIR transparent window for MLX90640 or other IR sensors?

Sensors Imaging
1

Anyone got any suggestions for LWIR transparent material for sensors like the MLX90640? My use case is as a crude cloud detector for my telescope.

Unshielded, I can get some good indications that there is significant water vapor - humid air or clouds - in the sky, even if it’s not visible to the naked eye. I’d rather not leave the MLX just flappin’ in the breeze or exposed to bugs, pollen, or bird poop; thus I’d like to put a thin sheet of something in front of the aperture to protect it.

2

This might seem silly, but a thin plastic grocery bag stretched over the sensor would probably work. Have used this with other infrared cameras.