I believe this is also known as ground cherries..that is what I found when I typed it into the Google search engine looking for sources. Try the google search .. it has some listings and also cultivation sites.

I used to have these in my garden. We called them husk tomatoes because of the papery shell that encased the fruit. When they turned a yellowish color or dropped off the vine, they were ripe. The fruit is sweet and very good. My mother made jam with these. Inevitably, some of the fruit stayed on the ground, and every year they reseeded, so you'll only have to plant them once.

I believe Thompsen & Morgan may carry these, and sometimes you may find the seeds in your local garden center.