Finding replacement firing pins and springs for the ATI Cavalry can be challenging, as the shotgun's parts are not widely interchangeable with generic parts, and the original manufacturer is often an importer, not a maker. Lamar pins will not fit unless they are specifically made for the ATI Cavalry (Kofs Cavalry SX) model, as firing pins are not universally compatible.
Here are recommended sources to help you find the correct parts:
Recommended Sources for Parts
Numrich Gun Parts: This company specializes in discontinued and hard-to-find gun parts. They list parts for many ATI models, including the Cavalry O/U Shotgun. This is likely your best option.
FiringPins.com: They manufacture a wide selection of precision firing pins to exacting OEM specifications. Check their extensive online catalog for a match to the specific ATI Cavalry model.
Brownells: A major supplier of gun parts and gunsmithing tools. Search their inventory for the ATI Cavalry or related models to see if they stock the necessary components.
eBay: You might find individual sellers or small parts suppliers on eBay who stock rare or used parts for the ATI Cavalry or its equivalent models. The ATI Cavalry is manufactured by Kofs in Turkey, so searching for "Kofs Cavalry SX parts" may yield additional results.

Hi Leroy and welcome. Check "Firing Pins" for ATI Calvalry Sport models at Phone 888-463-3603 - Mon - Sun / 9:00 AM - 5:00 PM or by online inquiry here; -- firingpins.com/contact/ ------ Cheers, stay safe and good luck! Rowe Tactical is another good source: https://rowetactical.com/shop-now/firing-pins-manufacturing-services/

Good evening to you!! I looked on numrich gun parts. They didn't have them. Brownells didn't have them. Firingpins.com didn't have them either. I suggest calling ATI back and see what they recommend for a replacement. 800-290-0065. Hope this helps. Have a good rest of your day.
🇺🇸🇺🇸 'Merica' 🇺🇸🇺🇸