The only thing custom I can afford is something i did the customizing on!!
Have a friend who hunts elk a lot and he has a Christensen Arms rifle. He loves it. Light weight and VERY VERY accurate. Not sure what he paid but I think it was around 4,000.
Another I would love to have is one made by Ken Jarrett. I have seen them but never shot one. Great looking guns that shoot lights out.
If you are just looking for a barrel you might want to get a hold of gary Schneider of Schneider Rifle Barrels. I dont believe he has a web sight ( I could not find one) but a lot of Long range shooters use his barrels including the best of the the best. The USMC Snipers use Schneider barrels on their rifles.