Austin,
The part that is broken is the operating handle.
You can find them on Gunbroker, Numerich, and from time to time on Ebay.
There is quite a bit of work to replacing it as you have to disassemble the entire bolt.
It would be best to have a qualified gunsmith do this as he can check for other tell tale signs that may be occurring that may have caused it to break in the first place.
Will