contact Lawton Machine we use their barrels as much as we can and they are as good as any also check with Rock both make top quality match grade cut rifles barrels.
Any barrel maker can make you a barrel in whatever bore diameter/twist you want, I suggest you consider a cut rifled barrel with 5r rifling, Rock, Bartlein, Kreiger, and there is alot more.
I just placed an order with Hart. He has few in stock and told me two to three weeks for delivery. Waiting on fluted, 5.5 contour 26" 1/10 for my 300 wm.