TBH, I'm not sure you can get them anywhere, unless you want to buy the pickups & retro fit them to your 4003.
You could maybe buy a metal bridge pickup cover & cut a section out of it, but you'd need to mount it onto the pickup base plate to stop it wobbling around (with the height adjustment spring between it and the mounting ring).
You could maybe buy a metal bridge pickup cover & cut a section out of it, but you'd need to mount it onto the pickup base plate to stop it wobbling around (with the height adjustment spring between it and the mounting ring).