1) Beattie McGuiness Bungay, Bartle Bogle Hegarty, Higgeldy Piggeldy Niggeldy… They’re pretty good but you’ll need deep pockets.
2 ) Look for a freelancer. There are some good ones out there. Good luck!
3) Write it yourself. But you’d be surprised how time-consuming writing can be, and your own work is sure to pile up. And if the end result is not really what you wanted, can you afford to do it all again?
It’s better to leave it to the professionals.