The important thing you should add to your posting is what price range you are looking in. I can't tell if you want an original or a repro, but your price range should reveal that.
I can't tell you how many people have contacted me or talked to me at shows wanting me to find them a genuine, 12-pounder Napoleon Civil War Gun-Howitzer, M1857, and they want it for $5000.00 or less. I'm not kiddin'! They won't get one for that price unless they find a scrap dealer selling it for scrap value alone, which is somewhat unlikely these days.