Ah, yes, Tenite. Our introduction to "The Wonderful World of Plastics," our generation's great--and, you better believe it, lasting--"legacy." (Need good luck? "Tock, tock, tock--Knock on Tenite"!).
Does anybody else have all the variations of the classic Stevens Model 124?
Seriously, I think SOME 311 parts might work, but you need to look for the earliest you can find. The 311 series went through a lot of modifications over its many years of production, some worthwhile tweaks, some just cheapening of production. But an early one might be close to your gun.