This is where we ordered our boat name lettering and I also ordered a custom sticker for my Board. They did a great job and you can choose any type of lettering, font, style color you wish. And they're cheap.
You'll need to go to the "vinyl lettering" section in order to be able to really customize it. The registration number section has to follow Federal regs and only allows you to choose the color.
Good luck! http://www.speedysigns.com/lettering/