The Roush operation in Livonia Michigan has a boring mill that should be capable of doing that for you. They have an extensive establishment there and many phone numbers, but (734) 779-7006 should get you started.
I'm actually a great fan of Barry's operation, but doing the proper job of such a task takes a GREAT BIG machine. Roush's is of such a size you have to climb up on it to be able to reach the working area.
KS