I ordered a new dash trim kit for my 1983 900S from one of the MIMO distributors selling on Ebay, and after waiting a month it's arrived today. The seller has been de-registered off Ebay in the last few days but not sure why yet.
Anyway, I'm pleased it's here and when I install it I'll get some pics as it goes along. It's intended for use in 87+ c900's so it has extra bits for the switch panel and the right-side piece for the main dash has an extra hole where there isn't a hole in the dash in the 900S (situated behind the washer/wiper switch). I'm not sure if the later c900's had something in that space but it's blank in my car.
Craig.