Sorry for the previous post, I couldn't resist.
I had a look around a few parts suppliers, The only thing I could dig out was a cover with holes, from a UK supplier.
Here's the link anyway:
http://www.touchstonetonewoods.co.uk/ttwp53.html
part 5164, it's listed 2 above the subtitle 'Jack Plates'
Also, here's the Schaller page of pickup covers.
http://schaller-electronic.com/hp122...ckup-Cover.htm
Note the picture is gold, but Schaller will supply covers in cream.
If you have a local Schaller supplier, you should be able to order a cover through them.
Having said all that, you may find the Schaller cover doesn't fit: I don't know the size of the pickup on the Jack Cassady bass.
The other option is to contact Epiphone, and see if they will supply you with a replacement, or at least tell you where to get one.