There are coat patterns at knittingpatterncentral.com and garnstudio.com. I recently made one of the garn ones (mid calf) but opted to make it carcoat length.
Try, Book 1: The Knit Stitch by Sally Melville,
the Einstein Coat. You can make it as long or short as
you like. I made the child's size for my granddaughter,
it's easy with minimal finishing. It came out beautiful!
I bought the book since there are more things I'd like to
make in it but you can also check the library.