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

The OP has a $5K table that can't keep maintain a reasonably steady 33.3, as is-stock?

I would demand a refund.

different power cords on a turntable makes no difference......

Yeah, right. 🙄

lewm, I’ll admit that if you redefine outside the signal path to mean in the signal path then yes, you are right. Word games aside the point is all these things really do matter. And not subtle, but a lot.

OP- full disclosure. When talking about platter, plinth, motor, bearing, motor housing, etc. and saying "all these things matter" there is the possibility of misunderstanding. "All these things matter" not because someone said somewhere once upon a time. "All these things matter" because they have each and every one been tried, one at a time, and been shown to matter. Its how the Miller Carbon Turntable was built.
DYODD. https://systems.audiogon.com/systems/8367

It makes a difference. When I bought my Technics SL1200G I started with the supplied power cable. I had Rob Fritz from Audio Art build me a cable for the turntable. 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.

Please notice OP there is a pattern. Those who have actually tried and done all say it matters because they know from experience it matters. Those who have not done make grand pronouncements devoid of any actual knowledge, let alone experience. Its rote repetition. Repetition without comprehension. The proper response to them is, "Polly wanna cracker?" As opposed to stereo5 and me to whom its, "Well now, good to know, I will have to look into that. Thanks!"