Wondering why you want a back cover? I ONLY have the front cover on the iPads I've owned included my iPad Pro 10.5". The back cover is very durable. I even write short notes with pencils on the back cover which easily erase off without leaving any marks. I AM concerned about the screen though and have used covers on all my iPads.
As for the "pencil", that have remained in my drawer since I bought the iPad Pro 10.5".