Marmolade, you might find free stuff at Freecycle.org. It’s a series of yahoo groups intended to let people give away stuff FREE! There’s likely a group near you.
You can check craigslist too.
Other than that, you might find pieces at the thrift shops, but many folks are jealous of their old cast iron (the older the better).
So you may end up buying your own new. It’s not expensive. Lodge makes a good line. You can often find pieces at hardware stores. For example, Fresno Ag carries many unusual pieces from Lodge. They have cactus shaped cornbread pans, LOL.
Thanks for the Freecycle suggestion. I’m sure there is one in my area, but will have to look into it more.