Agree with BarbInLouisiana ..... if you have a Mariner's Compass pattern you like at any size, it can be enlarged at a copy store.
If you go this route, there's a couple things you might want to keep in mind ...
* A nice block in a small size doesn't always look as nice at a considerably larger size. What I am meaning is that it can be very detailed and complex in the smaller size, but when enlarged, there may not be enough detail for you to be happy. Colouring in your enlarged with crayons or markers might be a good idea, before starting to work with fabric.
* Because you want a block so large, look for a copy place that can do large size paper copies. Too messy to start gluing sheets of paper together. Better to have what you want on one piece of paper.
All is possible ... this can be an incredible project!
Good Luck!