My chicks love baked, crushed eggshells. I put them in the blender on low-to-medium and they're ready very fast!I second what kcan2 says above. Feed Flockraiser or All Flock once you're out of layer feed, with oyster shell and grit on the side. Thats the basic solution, although folks have variations. Also, you can feed their egg shells back to them. I like to bake them in the oven to kill any germs especially if I get eggs from any other source. But after baking, I crush them up, and then they can eat the egg shells like they eat the oyster shell.
As far as search terms I don't know, you might try "rooster, flockraiser, all flock, feeding, calcium for rooster, rooster feed?" Make sure you search the forum that deals with feeding, or you can navigate to that forum, and then run a search and tell it to search within that forum. There are links that the site suggests to similar posts on the bottom of each thread - I've found those to be super helpful, kinda stumble upon a lot of great related info that way. Also the What's New button at the top - someone asks this question off and on pretty regularly.
Good luck!!!