Pretech makes a 6-pot caliper for the Rocket. You'll want to check to ensure ABS compatibility.
Brake Calipers | Motorcycle Brake Calipers | Racing Brake Calipers | Engineering | Pretech, Reading, UK
But unless you're taking your Rocket to the track and doing repeated high-decel braking and having your brake fluid boil, you should ask yourself exactly what you're looking for. The stock brakes are good enough to modulate and lock up the wheel / engage ABS, so what would be the benefit of larger brakes in even the most spirited street riding? Larger calipers and/or discs just add cost, complexity, and increase unsprung weight. In stock form, the limiting factor in deceleration is the wheel friction with the road, and the weight.
Use the Lotus philosophy: "Simplify, then add lightness." You can start by replacing the stock exhaust system to drop 50 lbs.