Try gunpartscorp.com or auctionarms.com or go to a gunsmith
Try www.gunbroker.com
Bobs gun parts sometimes has wood stocks for $150. Chaote has a synthetic stock for $66.00
Sir I would try ithacagunsusa.com and ask them if they can help you. Ithaca guns is now located in Upper Sandusky Ohio. Sarge
http://www.gunstocksinc.com/web_pages/Plate-pics/Ithaca-Stocks/Itaca-stocks.htm
i saw a used one on ebay but you can contact Ithaca Gun Co. directly
Remove stock from shotgun
To remove the stock from an Ithaca model 900 SKB shotgun, first ensure the firearm is unloaded. Then, locate the stock bolt, which is usually found at the rear of the receiver. Use the appropriate tool to unscrew the stock bolt, and gently pull the stock away from the receiver. Be cautious not to damage any components during the removal process.
I have been looking for a synthetic set also. They don't exist. I've even tried the new Ithaca manufacturers. No luck.
No one.
Try e-gunparts.com
443-108-160wb
I have one for sell in very good condition.