Flyht does have a webpage on the WVSS-II -
https://flyht.com/weather-sensors/wvss-ii/ There is also information at the spectrasensors.com website and elsewhere.
https://www.spectrasensors.com/media/files/None/WVSS-II-Spec-Sheet-Jun-2012.pdf The spectrasensors pdf is quite informative, with a lot of detail, a line drawing and a very good photo of the package on page four. The document is dated April 2012, no idea if the device has undergone design change since then. The picture at Flyht's site looks identical for the component shown and I seem to remember a low res version of the SpectraSensors picture at the Flyht site recently.
You may notice Flyht's description has a lead sentence typo that needs fixing - "FLYHT-WVSS-II uses Tunable Diode Later Absorption Spectroscopy (TDLAS) technology" - should read "Laser", not "Later".
No "brochure" on the website page of product brochures as yet.
External mount, with the rest inside.
A 22-page slide show exists, contains pics of the internals. Looks like it could use some updated connectivity options if the picture is current.
https://www.slideserve.com/sanjiv/water-vapor-sensing-system-wvss-ii 
Flyht's Tamdar link
https://flyht.com/weather-sensors/tamdar/ has some good information.
External mount, with some of the internals visible in this display model.
