Hi Weeksi!
I am looking for exactly what you are asking and I have found something almost perfect...
It's a NZ brand; they make tailored covers depending on:
- type of rack (wall mounting, tow ball, etc), brand and model (Thule...)
- way to fix the bikes (first with front wheel looking to right or left, handlebar straight or rotated 90º, etc)
- if non carrier or small/medium or large...
It seems to fit as a glove, waterproof, well closed over the rack, easy to put on.
I did some questions about noises when driving, wind resistance, and visibility of rack's lights and plate. They answer no worries about noises and wind due to no flapping, no speed limitations, and sent me a picture with not exactly same model, but quite similar, where lights and plate where well shown due to an open velcro strap in the below side.
But although EU and NZ have an agreement free trade since last year, so no importing taxes, international shippment cost 150-200 euros plus VAT (21%) so final price is expensive.
www.ocdcoversandracks.com