Welcome to the board!
The pickguards for Warmoth bodies may not be an exact retrofit for Fender basses, so buying a premade from an outside vendor may be tricky.
W has a pretty good selection of pickguard material but alas there is none of my least favorite (gold) available.
General reminder: Warmoth is a parts company, they do not assemble complete guitars there. (I wasn't sure if it was clear based upon your post)