I believe there are only 1 or 2 companies in the States that make tunnel diodes anymore and this site explains how to make something quite similar at home quite easily. Figured someone here might find the link as interesting as I found it to be.
http://www.sparkbangbuzz.com/els/ntype-nr-el.htm
http://www.sparkbangbuzz.com/els/ntype-nr-el.htm