I use EMG's in front of the aguilar obp3. I'm not sure if that preamp is an option for you but I do recommend it.
Is your bass the three knob or the four knob version?
Rothstein guitars makes prewired harnesses. Link
here.
There is another company that makes a bolt-in preamp with plate, but cannot recall who it is. The Rothstein may be bolt in but am not sure. Nor have I ever heard it.