That is a very good looking bass you have there. So I wonder what is worst:
1) Getting minor scratches in the clear coat
2) Altering the clean design with a pickguard (which will also require new screw holes, i.e. non-reversible modification).
My option would be to cut my nails short and leave it clean.
IF you still decide on a pickguard, my vote would go to a three-ply black with white edge. somewhat like this P-bass:
This bass may have what you are looking for: http://www.fender.com/en-SE/series/a...bwb-pickguard/
Contact your authorized Fender dealer for availability.
Or search on ebay. I searched for "jazz bass 5 string pickguard" and found these among others: http://www.fender.com/en-SE/series/a...bwb-pickguard/ http://www.ebay.com/itm/True-Custom-...item1c36ef06d9
All standard jazz bass pickguards are made to mate with a control plate for the controls, which means that you may opt for a pickguard without a control plate.