I don't think such a service exists. I think I found one legitimate one which cost $40 per dupe or something like that for which cost I purchased some 4x5 Fujidupe film (now discontinued, check ebay or use the Kodak Equivalent) for cheap and contact printed them with the dichro enlarger. On the 4th 40 minute process length control strip I decided maybe I'd just project the originals. It can be done and is probably easier once calibrated, but it's a pain.
The main problem you are going to run into is that both Fuji & Kodak have discontinued 70mm dupe film. Unless things changed at the last minute, 4x5 is gone as well. I'm sure there are labs out there that have some dupe stock left. Is time an issue? If not, PM me and I may have a possible solution.
"Everytime I find a film or paper that I like, they discontinue it." -Paul Strand
You might look for a Slide duplicator, Bowen's made an excellent one in the UK capable of duping 35mm-5"x4", the Illumitron was a specialist unit with built in flash illumination, it also had an adjustable contrast control system so you could dupe onto conventional slide films. (Worked like pre-flashing to control the contrast).
According to Kodak's website and B&H, their Edupe film is still available. 4x5 is fine. I am trying to duplicate MF stereo pairs. 4x5 seems like it would be easier to work with (sheets) vs. a roll for contact printing. I guess I would need an enlarger to do it myself. How much would I expect to pay for a 4x5 color enlarger (assuming I will need color filtration and test runs to get things right for each pack of film). Of course, if Edupe only has a year of life left in it, I wouldn't want to set up this whole system would I?
You can dupe them yourself with a fairly minimal setup. It will be an initial investment, but if you will be doing it a lot it might be worth it.
Another option is scanning the chome and then re exposing a new one from the file using a film recorder. This also lets you do any necessary spotting, contrast tweaks, and/or color correction in the computer. The one I am used to using (Polaroid) has backs for 35mm, medium format, and 4x5.
DR5 offers the film recorder service. I am not sure if they can do 100% analog copies. I'd give them a call.
I know that nothing interesting or extremely useful like this can be done at the big lab in L.A., A and I. They are a decent lab and I am glad they are there, but they only offer very run-of-the-mill services. If I could easily get analog transparency dupes made, I would shoot chromes almost entirely for color.
"Truth and love are my law and worship. Form and conscience are my manifestation and guide. Nature and peace are my shelter and companions. Order is my attitude. Beauty and perfection are my attack."
If you need another chrome for projection purposes then you will have to copy it onto some other chrome film. If there is any issue of storage then it might be easier to just copy it onto color print film. Corrections can be made when the color negative is scanned. Without some kind of contrast control, using regular slide film will cause a build-up in contrast. You will need to experiment with any duplication film to have the right EI and color filtration.