Greetings,
The short answer is nowhere. Chapparal Arms only makes their 1873 in 45 Long Colt, 38 Special or 357 Magnum. The only modern reproductions I have seen in 38-40 were made by Uberti and that was some time ago. You might be able to get one on special order through Cimarron Firearms in the states. Good luck.
With Greatest Respect,
Matt