Platforma (vertical ipad messenger bag) from Strotter may work for you. Has space for everything you listed, plus turns into a mobile desk so that you can work anywhere, using both hands to type - even while standing up - no need to hold the iPad. The bag also converts into a slim sling-type backpack. Takes only 2 seconds to change modes, so to say - from cross-body to backpack to mobile desk. It is not too big, and not too small. Extremely well made, lifetime warranty. Watch the videos on the website to see how it all works (you will be surprised, promise).
Disclaimer: “I may receive some form of compensation, financial or otherwise, from my recommendation or link." (I am the designer of the bag and the founder of Strotter.)