They are grown in Mexico and in China. In North America and in the UK, they are very hard to find fresh, though you may find them canned in ethnic stores.
Tejocotes are used in making a traditional Mexican Christmas punch, served hot. Every Christmas, US inspectors at the Mexican border prepare for an onslaught of smuggled Tejocotes. The shipments are seized for fear of insects on them. There is as of now (2004) no significant production within America.
Substitutes
Kumquats, dried apricots, plums
Literature & Lore
The Aztecs called Tejocotes “texocotl”. From Tejocotes, they made a preserve called “texocotzopelloti”. US Customs literature is one of the few places where you will see them called “Hawthorne Apples.”