The logical place to look is at your local gunsmith's shop. You can probably get the parts you need online.
Go to the "ithacagun" dot com home website for parts.
By the serial #
Where can you find parts for your Charles daily shotgun
You may contact Ithaca arms and they will date your shotgun for you.
Your serial number indicates that your Ithaca shotgun was made in the year 1920.
Try any local gunsmith or contact the company Ithaca Gun Company, LLC 901 Route 34B Kings Ferry, NY Website Ebay. All kinds of gun parts. or go to Numrich gun parts on the web.