Finding Replacement Parts

I have an old plastic watering can that I want to use again this year. The problem is that the head (not sure fi thsi is the correct term) is missing. I really don't want to buy an new one. It would be a waste and take up more space in the landfill - sure its full of things that needed just one thing to be useable. There are also several things in the house that need only one or two parts. Like a nob on the stove.

Has anyone else successfully found parts for things not readily found in the store? I have already looked online with little luck.