For a case.. one of these is great. basically you need a 17 inch laptop sleeve. just make sure you check the inside dimensions.
https://www.amazon.com/gp/product/B01C8H1VX2/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
There are not many choices in that size, but shop around you might find one with more outside pockets.
For a pen case, get a fountain pen case. there are tons of great choices.