For what Apple’s 12" MacBook lacks in ports and power, it makes up for in portability and sheer beauty. Today only, first gen refurbs are marked down to $800 (256GB/1.2 GHz) or $900 (512GB/1.3GHz) on Amazon.
This being the first generation of the computer, it’s pretty underpowered for anything beyond basic computing tasks, but it that’s all you need out of a computer, I can tell you from personal experience that you won’t find a better machine for using on an airplane tray table. For context, Apple sells refurbs of the second generation for $1019-$1269.
I highly, highly, highly recommend you get the $900 model here. $100 is a bargain to double your SSD space, and in this computer, that tiny bit of extra processing power can make a big difference.