There are quite a few custom checker'rs out there.
Do a search and check some of the gunsmithing and custom gun sites/forum for discussions on who's who and critiques.
One that comes to mind is Sherry Abraham. She's in Oregon and used to checker for Kimber.
Here's her web-site.
Quite a few builders use her for checkering work. I have never senty out checkering work as I always did my own (not taking on any new work though)
Prices and patterns are listed there somewhere on the website.
Custom Checkering by Sherry Abraham
DTR likely sends his checkering out to someone like her (not necessarily her).
But if you want to pay 3 times the price, he might pencil you in.
Check on AccurateReloading.com
Several different forums.
There is one for 'Checkering' alone.
There are often posts for 'Who can do checkering for me?'
The Gunsmithing and the Custom Rifle forums often have a few 'Who to go to for Checkering?' discussions in their historys as well.