I think, what i can say is there are a lot of mini to big supmarkets that sell the things you mentioned; if you go out to piassa to bole or megenagae in all square of addis ababa, that is where i live, you would find.I have an anunt who made the same mistake and finally was saying "What a waste of energy and money". She found it in a very mini shope, close to home. So if you want go to those international hotels, which have inside their own supermarkets. Tell them to "google" it just click away to see what is there or not. Anyways i gave you two links that lists a bunch of them,
i prefer the second one, go through it