Not too sure about the choke... I suppose any cylinder smoothbore fowler and then you could have the end of barrel tapped to accept a Rem-choke or the like.

But these are very nice:
http://www.flintlocks.com/rifles04.htm Smoothbore fowler in 10 or 12 gauge.
www.caywoodguns.com English 12 gauge fowler.

Or if percussion is what you want:
http://northernrifleman.com/tab1/store/category/7vv4/Shotgun_Kits.html

These are the Pedersoli side by sides.