Yellow rooster is really good. Not sure why you're replacing it so often. Mine will go at least 100 sailing days and really do not see much deterioration. Will kink more when old but really still less "kinky" than most other mainsheets I tried.
I had lost a part on a 7 years old Jotag dolly and asked Intensity whether they had a replacement.
In less than a week I received the replacement part directly from Argentina, free of charge.
Above and beyond!
If I were you I would consider returning the new alu mast and buying a plastic one.
It's more expensive but it will probably be the last top mast you'll ever buy. The alu mast will eventually fail and rip your sail in the process.
In the meantime, used the fixed old mast or borrow one from...
Is the new mast you bought plastic?
The repaired one will work just fine and you should keep it "just in case" or use it for practice. It won't break where it was repaired.
You can also make a boom.
Definitely don't junk it.