If the bulbs we have are indeed 25W D5S then there currently isn't any other options other than the factory. D5S bulbs have the ballast attached to the bulb, so when you replace a bulb you're also replacing the ballast. Its one combined unit:
D1S bulbs are much more common in luxury cars, they use the same bulbs as D2S bulbs (the most common HID bulb) but they also have attached ballasts:
D5S projector housings have a different focus point than D1S and D2S housings, and they attach differently, so you can't stick a D1S on. You'd have to retrofit it, which requires removing the headlight, baking it to release the silicone glue to separate the front and back of the headlight housing, removing the current projector, and replacing with an after market projector (which will require cutting and drilling), then gluing everything back together.
I'm hoping the sport manual that I apparently don't have is the one you posted, because if we actually have D1S bulbs, we're in luck.