I can't help you directly, but I bet if you contact these people, they can:

Cape May County Beach Plum Association: http://www.cmcbeachplum.com/

Here's another link that might be useful. It lists Prunus maritima suppliers. I haven't looked for certain cultivars, but a quick check should be easy.

http://www.beachplum.cornell.edu/nurseries.html

Thank you for the information. I did not find these particular varieties for sale. However, I did purchase Nana and Ecos beach plums from oikostreecrops.com. I also purchased some blueberries from this company as well.

Has any one had success with Nana or Ecos beach plums or other named varieties?