“Best” is dependent on you.

Anker is quality, with a price to match and the 140w 737 is overkill for this device.

Baseus is cheaper, but less quality. Sometimes people report they fail, which might point to a QC issue, or user error doing stupid stuff like leaving their expensive lithium ion power banks in a hot car overnight.

INIU is cheaper like Baseus and has a great warranty. I love the 65w/26k mah one I have for this device, and I recommend it to anyone who goes for

Key things you need are 15v at 3a from a single port, using USB PD protocols. Most Anker batteries will do this, most Baseus ones will, and most INIU ones above 45w will too. If it has the magic 15v = 3a PD spell, it will charge the Deck at max speed so long as your power cord is also rated for that much wattage or more.

I use the Anker 26800. Caps out at 96whr which is very close to the maximum amount you can carry on an airplane (100whr for international flight). It has 45w output charging so it won’t drain the deck slowly as you play.