Vendors I've used has either of two printers, Laserjet (older technology) or Chromira.
Both need trained operators and careful setup.
You might do a search for fine art prints or exhibition prints to see if there is a vendor in your area. The ones I use are in California.
Jack
Would you mind sharing what the name of the business is that you use?
Charles,
The laserjet outfit was located in Florida but I no longer remember the name, that was for Comet Halley prints, about 1987?. Calypso used to do very fine prints but closed a few years ago. I heard there is a print lab in Santa Cruz that still uses a Laserjet but I don't know the name. Met a fellow that worked there when shooting Comet panSTARRS at Fremont Peak.
Depending on what I'm doing I use either Aspen Creek Photo or West Coast Imaging in Oakhurst, Ca. Two companies, separate facilities, same owner.
http://www.aspencreekphoto.com
Aspen Creek is an automated setup where you do all your own prep work, submit it electronically and they just print per your instructions and ship.
West Coast is a custom lab where you work directly with a master printer. Obviously this is more expensive, and takes longer as you discuss your goals and need to review proof(s) before final prints are made.
http://www.westcoastimaging.com/#intro
They print on Fuji Crystal archive papers which I like, also they offer ink jet prints, metal prints, acrylic face mounts, etc.
I've had great results with both. Obviously due to the higher expense, only special projects go through West Coast. They both offer specials regularly that reduce costs, so I tend to print in batches and take advantage if the sales. I also request them to ship flat, not rolled.
I'm sure some of the other folks here can offer suggestions on vendors they have experience with.
Jack