I would go to Numrich gunparts corp.They may be found on the web.
Condition? $200-$400
250ish depending on condition
Numrich (Gun Parts Copr.) has some Iver Johnson parts.
It holds 14 rounds in the feed tube plus one in the chamber.
20-125 or so
Numrich gun parts.
gunpartscorp.com has the best collection of Iver Johnson parts
These were made by Iver Johnson company. Try searching gunpartscorp.com under Iver Johnson,
== ==
Iver Johnson was created in 1871.
Iver Johnson ended in 1993.
Go to Google, select IMAGES from the toolbar, and for search term enter Iver Johnson double hammer shotgun.