Try CPA Rifles or Lee Shaver Gunsmithing, or the American Single Shot Rifle Association (ASSRA - I believe they have a classified section in their free forum). I will look to see if I have one. I 'inherited' 2 or 3 Stevens barrels of various ilk from my dad. If I have one I'm guessing it's not in good shape though. You may also just be able to have a gunsmith put a new barrel on it; I think both CPA and Lee Shaver could do that with an original-contour barrel. I learned to shoot with a Favorite and believe my dad had the original barrel replaced due to being badly pitted. But the barrel was round from breech block to muzzle and so may have required a new forend (maybe from CPA Rifles?). One of my nephews has the gun now or I would take a look. I will message you if I find anything. Good luck.
Thanking you generously for your input. Will wait to hear from you. My rifle is in 90%+ condition and still maintains case color, it is just 25 Stevens Rimfire.