Try Windsor House (311 Gloucester Road, Causeway Bay). There are 4 - 6 shops that carry Apple / Mac related products. They are on the 10th - 12th floor, I think. I've always shopped at Designer Group (
DG Lifestyle Store ) which is on the 11/F. But you might be able to get a small discount if you shop at Cablex, which is on the 10th or 11th floor.