I took a can of tuna, drained and cleaned out, and just cut the bottom off of it. It is the perfect size for making eggs for your own McMuffins. And, IMHO, work just as good as what you buy at the store does.
When cooking an egg in them, just use tongs to remove it once the egg is solid enough to hold its shape. I prefer to twist it around a few times to loosen the egg from its sides, then lift to remove.
I used to do that too until they quit putting a crimped flat on both ends of the can. It now has a rounded bottom. Takes all the fun out of life.