You can't... you will have to make them yourself or have a machine shop make the parts
Go to"krieghoff.com".
Need more info. Which manufacturer & which model??
Utica Firearms was a trade name used by the Simmons Hardware Company of St. Louis, Missouri on firearms they retailed circa 1900. It could have been manufactured by any of a dozen makers. Like any other 100-year-old tool or machine, parts are where you find them. You may be able to get parts that fit (or can be made to fit) from a local gunsmith or at a gunshow, but no one will have a catalog number for "Utica firing pins".
did you try mossberg shotguns for parts,the 500 is almost the same as your gun ?
I can buy shotguns in nevada, I am the terminator, I'll be back!
Look up Numrich at I think: gun parts inc west hurley NY
Parts for these shotguns are hard to find. EAA Corp carries parts for Baikal shotguns. A good gunsmith might also be able to help make some parts.
gunpartscorp.com
Check out gunshop.com,they got Lots of info on dbl barrel shotguns.
The value of these single shot shotguns is ranging between 45-130 dollars.
In Baltimore by the 7-11
try: gun-parts.com