I don't use a cover. I had a plastic cover that covered the lid and bottom, but it made the laptop heavier, and added enough weight to the lid that small movements in the laptop would cause the lid to move. IOW, the hinge isn't calibrated to handle the weight of the lid and cover combined.
So I took it off, and now just keep it in a sleeve when I'm not using it.
I use this beautiful leather sleeve:
Our best selling MacBook Sleeve. Designed to protect your laptop against bumps and scratches while looking slim and elegant. Handmade with premium real Leather & 100% wool Felt. Laptop Cases and Laptop Sleeves for MacBook Pro 14", 16" inches and MacBook Pro 13",15", MacBook Air 15".
www.harberlondon.com
The way it's sewn, they leave a slit that allows enough room to connect a charging cable while it's in the case.