Converting a 410 Derringer barrel to??

[DS94901]

Anybody know of a barrel "conversion" for one of the 410/45 long colt derringer kits? From my understanding, if built, these are illegal in CA because they are actually considered a short barrel shotgun. Was hoping to find an affordable way to chamber it for a round that would not also allow any size shot shell.

I sent a message to someone at trackofthewolf.com to see if they offer anything like this but my impatience has me looking elsewhere as well.

Do-able or not worth it?

[DS94901]

Actually just found this place but have not heard anything about them. Any experience or any knowledge if this would fix the legality issue if the insert was permanently attached?

http://shotgunadapter.com/

Obviously would need something rifled though