Probably better to replace the whole thing. No telling if the impact that broke the lever did any internal damage. They're not expensive anyway. Was it the stock original? If so, time to upgrade to a Pingel or similar better than OEM type...
You'll have to replace the whole petcock.. From what I can tell the OEM
petcock has been discontiued. You should have plenty of aftermarket
petcocks to choose from. My local dealer service guy gave me a used
one last week with extra nipple for vent hose hook up. He said it would
help it breath better... We'll see!