West Mersea Yacht club have some, Peter Clarke's Boatyard have some (the white buoys at the end) and I think Alan Bird has some. I am sure there are other owners but I don't know them. You have to be a member for the Yacht Club ones (obviously) and they are generally well spoken for - that includes some at the entrance to the creek and the head. The white buoys at the head of the creek at Peter Clarke's and I don't recall any spare ones this year but things do change. I would suggest a call to them. Give me a pm with your email address and I'll give you Alan's home number and you can ask him.