Any name brand that delivers 2.1A at 5v.

I like Anker, but currently use one from Ikea.

I would invest in a good cable too. Here is the one I use at home, and the one I use when I am traveling (I put the battery pack in my shirt pocket when using the short cable.) The right-angle connectors are awesome, and reversible!

I have tried multiple magnetic cables, but so far I have not had great luck with them keeping the Go fully charged. That may just be because I really went low-bid on them.

I have not had that problem. I tuck my cord behind the hard plastic part of the strap.

I also recommend 10 foot cord with a right-angle connector. The right-angle connector sticks out less and puts less torque on USB-jack.

Or, if you don't mind paying the same for a single, magnetic, 10 foot cable, you can reduce the chance of damage even more.