I love Rickenbacker basses, and like everyone else, hate the pickup cover.
I came across this at a company called RickSource.
Every 4000series player needs this pickup bezel. Available with a thumb rest built in.
They are made by a company called Tubeampology, available from them directly or from Ebay, though I haven't seen them discounted by anybody. I have "cove" model with thumb depression, nicely made. http://tubeampology.com/store1/index.php?p=home&mobile=0
Lots of people like them; lots of people don't. Guess it just depends how you want to play your Rick. For me? No thanks; don't want one; don't need one...I play mine between the pick ups, with a pick. But, if one of those doo-dads makes you love your Rick all the more? Play on...