Oil Pump

As I was breaking down the engine to paint it. When I took the oil pump off I discovered that it was broken The piece that slided into the block was broken off inside. The oil pump is two pieces, is there any way to just buy the piece that meets the block and slides inside.

No you need to buy a new complete pump. As an example Hughes has Melling pumps on for 62$. Recommend replaceing the drive shaft at the same time.