Ok, here's what I would do. Actually, here's what I did when I lived in Hawaii.
If all I had was what you listed above, I would do the following....
Make your shake with milk, it has some protein and other nutrients, butmost of all it just makes it creamy and yummy.
I would definitely blend in a Banana for the potassium.
For protein, two eggs. I know it seems like alot, but raw eggs are actually very good for you, and loaded with protein for muscle recovery.
Then, I would add some other fruits like pineapple or guava if you have any, they have potassium and other natural levels of electrolytes too. Just depends on your taste. A little coconut is good for taste too, but not very healthy, it has alot of fat, or is it cholesterol? Can't remember off hand.
Powdered milk is ok if you want it creamier.
You shouldn't need to add any salt, since most foods have a little natural sodium in them.
If you want it nice and cold, blend in some crushed ice to make a chilled smoothie out of it.
-fruits like pineapple or guava etc, to personal taste.
-A little sugar if you like, to help restore glycogen.