What model ASUS? The black plastic part missing isn't going to cause the Chromebook not to charge. However if there are bits of plastic blocking the insertion of the power plug fully into the jack then you may have problems.
I bought screwdriver set many years ago from Harbor Freight. Something like this : https://www.harborfreight.com/33-piece-precision-screwdriver-set-93916.html
The keyboard for the X140e is the same as the one for the X130e and the X131e and the X121e.
It is FRU 04y0379
Buy the keyboard on eBay.