I've searched high and low... various forums, posts and websites. I've even been into my closest Lexus dealer who could not offer any support, or official part numbers required to purchase 16" winter steel rims for my CT200h.
A quick visit to my local TOYOTA dealer (no Lexus dealer associated with them) proved very useful, and I have been provided with an official Toyota part number which fits my current 2018 CT200h perfectly. VERY helpful folk. These are manufactured by Alcar, but sold by Toyota:
Toyota Part Number: PZ419G0691ZA
Rim: 6Jx16 ET45
Tyre Size Required: 205/55/R16 (H for winter tyres, V for summer tyres)
Centre Bore: 54.1mm
Homologation document: https://www.toyota-tech.eu/aimupload...2XT0189-02.pdf
I paid approx £220 for these rims (correct as of Jan 2019).
I required different lug nuts, therefore I purchased some from Amazon which are exactly what the manuacfuter specifies:
Thread Size: Taper Nuts M12 x 1.5 / 10.9
I did not opt for TPMS sensors... however TOYOTA do a winter wheel TPMS package for approx £100 (correct as of Jan 2019) which in theory should work (I would need to confirm part numbers first).
Now all you have to do is select the winter tyres you require. I have gone for Goodyear Allseason Vector Gen 2 - quieter, smoother and better MPG than the stock summer Yokohama Decibel E70 tyres (which came fitted to my standard 17" wheels). 17" wheels should have been an option, not a standard size in my opinion. The car rides a lot better on 16" wheels... and should not have been a factory fit option (in my case) with a 3 month wait.