It seems like brake discs from an Audi TT 3.2 aren't too far off. They are 334 mm diameter, 32 mm thick and 35 mm height. They only problem is that they are 5x100mm PCD and a 65.1 mm centre bore. Drilling them to 4x108mm seems a problem as the disc has more than just the 5 holes in itm which doesn't leave much room for drilling more holes. Besides that I don't know if the 1.8 mm too big centre bore would be a problem.

Would it be possible to get brake discs suppliers to drill a blank disc to 4x108mm and a 63.4 mm centre bore?