All I can find are the #2 tang sights and they are for other rifles.
I believe it is out of production and you will have to find one used. Gunbroker has had them and they are pricey, asking all the way up to and over 200$. Since I have just learned what these are worth, I will start shopping for another nice model 12 Rems with a tang sight, since it probably would be a steal.
What have you got into that rifle? BTW that model is my first gun, handed down from GPop. I still have it.