I have a pair of the WH-R560 wheels which I assume are very similar to yours. Unfortunately, the spokes appear unique. They are straight pull bladed types with the heads at the rim and the nipples at the hub. I'm not sure what the diameter or threading is because they require a specific nipple wrench, not one of the common sizes. Even the lacing is unusual; 16H radial in front and 20H, radial ds, 2X NDS for the rear.

Mine have been perfect for over 10,000 miles but I expect when something breaks, they get replaced, not repaired. As FB noted, such is the problem with "exotic" wheels.