Im fairly sure MIM basses (or at least the ones i've had) have the split-shaft imperial pots. Which in that case, most knobs will fit on it!
Your standard ones for split-shaft will push on with a bit of resistance. The ones designed for solid shaft will slide on and then youd set it by tightening the screw.
In fact, i changed the plastic knobs on my MIM jazz to the chrome solid-shaft knobs. So i did the exact same change you were looking to do
Edit: For example, any of these will do fine (even though they are designed for solid shaft). http://www.guitarpartsresource.com/g...arrelknobs.htm