You're not going to find a cheap 5 string jazz pickguard. I've looked myself for mine mostly what I found were around 50 bucks. Best thing I could tell you is to buy the material and cut it yourself
I found one on Ebay for 40 (including shipping) but i was only looking to spend like $25 or $30. Could I buy a 4 string pickgaurd and cut it so the pup can fit?
it wont fit at the neck either. I also believe the body as whole is larger than the 4 string so I doubt the screw holes will line up.
Fender Jazz V tort pickguard at musicians friend. $29. Same price at guitar center. http://accessories.musiciansfriend.com/product/Fender-J-Bass-V-Pick-Guard?sku=364898
The Fender Jazz V deluxe has a smaller pick guard than the Fender 4 string Jazz which has a different screw pattern and size than some of the MIM and Japan basses etc. The best site I've found to date for 5 string and other pickguards is Chandler guitars. But unfortunately tort will run you in excess of $50 if I recall correctly. If you already have a pickguard (but not tort) you might try a local luthier to see if they can cut one for you, but I'd bet it will be nearly the same price or maybe more.