Tracy,
Dimetrics makes such a machine you are looking for. I don't know who to contact (other than Dimetrics), but a couple of years ago my employer looked into getting one. It welds from root to cap completely with this unit and, if it is a specific diameter you will be welding, than it might be feasable to rent one.
While we did not end up renting/buying the GTAW orbital wire feeding welder, I got to run it for a week or so on some carbon & stainless pipe. It does a flawless weld, but you need a skilled person to operate it because the controls you have to monitor require someone who knows alot about welding in order to make the right adjustments. Also, you'll need a facing machine which put a "L" bevel on the pipe as the joint is configured so that you'll get a awesome root pass with the pipes being butt up tight with no gap. You have to see it to understand what I am talking about, but like I mentioned, when the thing runs right.......I have never seen a better looking weld.
My employer decided not to get it because we change diameters so often and because of the skill level required to use it, because like I said, they will have to able to know what parameters need adjusting to make the right ones.