Serial number 33047 is one of the last lathes built by Sheldon in 1975 maybe a little later, according to the Serial Number Reference Book I have. John Knox may be able to date it a little closer, just have to check and see.
There is a company up in Rockford IL called Bourn & Kouch that owns what is left to the Sheldon Machine Co. They stock very little in the regards of repair parts. That damaged gear will probably cost you around $600 from them. Your best bet is to match it up to a Martin Gear or Boston Gear, modify it to that configuration and replace with that. I've made similar replacement parts from stock gears for the Sheldon lathes I have owned over the past years.
BTW- Nice looking lathe you have there. Sheldon lathes are sweet in my opinion!
Ken