There are a lot of places which sell them. Here's a 6'7" long, 14AWG Shielded power cord for $9.
Or go with the 6'7" (2M) 16AWG Shielded for $6.58
These are an upgrade from what many companies include as stock power cords, some being just simple 18AWG unshielded cables.
Unfortunately, I do not recommend the linked Volex 17604 (14 AWG) and 17602 (16 AWG).
I really liked the sound of old school Volex 17604 years ago, but now Volex cords are sourced from various
Asian oem's and sound nothing like the original Volex. Yes, I have ordered a bunch of them, and they sound quite meh.
The old school Volex was great because it seemed to do the least harm to the sound and not change the overall tonality of the component
much while helping out with detail resolution and richness still.
Many expensive audiophile cords that use overly heavy AWG wire (especially for SET) and/or go overboard with exotic wire/plug materials
or too-heavy shielding change the overall tonality and signature of the component too much IMO. In fact, I have the original Volex on
my SET currently after it bested much more expensive cords for sheer "do no harm" neutrality.
In this photo, the top Volex is the more recent versions to avoid, identifiable by nickel(?) plug blades and harder/shinier jacket material.
he original good Volex has brass-color blades and thicker/softer jacket. Volex17604OLDvsNew
, on Flickr