MIM Fender Precision Bass Junior with single volume knob

Tried searching without much luck. Though i know that the info is here somewhere.

I have a small MIM Fender P bass Jr. that I picked up years ago.
Been customizing it and want to do something with that volume knob.
There is no tone knob, and i like the simplicity of that. But I'd like to take it further and replace the stock pot
with a push-pull to enable switching the pickup into series mode. I am open to other suggestions too but i think this is what i'd do.
Any recommendation of a decent push pull pot to use for this? and perhaps a diagram of how it should be wired?
I do have an old push pull pot but it's 500K and i think I should go with 250K here.

Thanks for any help.