Looks like powerslot has larger diameter roters for the front for $600:
http://www.promotiontuning.com/Merch...formanceBrakes
AND for the rear for $400:
http://www.promotiontuning.com/Merch...formanceBrakes
But they use the stock callipers.
I haven't found larger calipers by themselves anywhere.

Personally, I would rather just go with the StopTech full upgraded kit, even though they aren't actually larger:
http://www.promotiontuning.com/Merch...formanceBrakes
Their only $600 and come with stock sized slotted roaters, pads, steel braided lines and fluid.
So there are a few options out there.