Rebecca,
I haven't seen anything close in the local nurseries. How big/what use are you looking for? single small tree? Clump form hedge?
Closest are the Cornus oficinalis. Commonly referred to in ornamental circles as Cornelian cherry. Has a 1/4"x3/4" red fruit small pit. Good for pies. The occasional specimen has sweeter fruit with less astringency. Seed grown, self pollinating. I have one and has been easy to keep in bounds @ 10'. Just pruned it once in last ten years. Partially under awning, full afternoon sun. No supplemental water. Great plant. I see it being used extensively as a mixed understory/ filler/ border plantings at six flags amusement park, gurnee, Illinois. Some fruit were pretty sweet, others not so.
Yes, I brought the sweet seeds home.

I visited the Chicago Botanical Gardens this past weekend, and they had a "Cornus mas" in their heritage garden. It didn't have a varietal name. The fruit looked like a cornelian cherry dogwood at the Allen Centennial Gardens in Madison, WI (though I don't know if those are labelled with a varietal name either.). Chicago's was a single-stemmed small tree, and Madison's is a multi-stemmed small tree.

Rebecca,
Take a look at OGW
http://www.onegreenworld.com//index.php?cPath=1_26
Maybe they can get it for you.

I know this thread is a little old but I thought I'd chime in. The only sources I've seen for C. mas "Nana" are....

http://www.vanooi.nl

http://www.divaplant.de/mediapool/62/623015/data/PDF-Listen/Gehoelzliste_Herbst_2013_-_Lunaplant.de.pdf

or a good discussion of it here....

http://www.baumkunde.de/forum/viewtopic.php?t=4691&highlight=Cornus

Google chrome is a good browser to view these sites in as it has a built in translator.

Good luck,
Little John