Hello!
If, like me, you got hold of Humble's recent GameDev Software bundle, then you probably have a copy of Pyxel Edit. Because palettes are saved in the .pyxel files that the program produces, I've stuck a couple of them on Google Drive with the correct palette for PICO-8 users.
The resulting spritesheets can be exported as PNG files for importing into PICO-8 - just be sure to use the 128 x 64 version if you're not wanting to overwrite the map area of memory.
128 x 64 version
128 x 128 version
For some reason, when you click the links, Google Drive brings up an unpacked preview of the .pyxel file - just click the "Download" button at the top-right of the window, and they should download just fine.
Full credit for the palette RGB values goes to Roman Zolotarev and his handy-dandy palette page.