How to upgrade "power cord" on turntable with wall wart?

Try upgrading the power supply itself by getting rid of the wall wart altogether using a linear power supply with proper voltage and often adjustable to fine tune.

Once I inserted it into the system, there was an immediate and noticeable increase in PRAT. Going back to the stock cord, the PRAT diminished noticeably.

How can you explain it ?
I bet you believe in fuse upgrade too

The each of us has to end up like this dude in Japan

Millercarbon wrote, "...if things outside the signal path can’t matter then why does the turntable matter at all? Platter, bearing, tone arm, motor- whole thing is outside the signal path. Yet someone with no experience just said emphatically it can’t make any difference."
The premise of the statement is patently false.  The turntable matters very much, BECAUSE the platter, bearing, tonearm, motor (and the mode by which the motor drives the platter) are all IN the signal path in the sense that noise, resonances, speed irregularities, alignment, etc, all obviously do color the SQ.  I am sure Millercarbon would admit this is the case, if he were to have a second thought.  This is quite different from the function of the power cord to a turntable.  One could argue that the power cord cannot affect the sound, so long as it is of sufficient gauge to carry the current drawn by the motor and so long as contacts on either end are clean.  I've thought about this issue and even experimented with different power cords. So far, I have never heard a big difference mediated by a power cord.  If the OP's turntable has a wall wart power supply, then I agree with someone else who commented that there is more to be gained by upgrading the power supply.  But that job requires some sophisticated knowledge of electronics.  Most vinylphiles are not capable of it, so they/we resort to flipping power cords and telling ourselves we heard a big improvement.  Notice, it's always an improvement, never a backward step.

I too, agree that the power supply itself is much more important than the power cord for TT's.