Farkle and Accessory manufacturer Wunderlich have really gone over the top with this accessory, see through valve covers for BMW R1200 models. At this stage they are only available for air cooled BMW R1200 models, not the water cooled R1200’s.
There doesn’t seem to be any video of these fitted with the engine running, but here’s what they look like on a V8.
Now see through heads would catch a few eyes and make your GS stand out more at night.
I found some footage of these running on a BMW 1200.