Vermiculite isn't easy to find in small bags. Check around local garden centers in your area. I had to visit several before finally finding a place that carried it in small bags.
Be careful misting the eggs. It can promote mold. It's better to set up the box with moistened vermiculite (1 to 1 ratio of water to vermiculite by weight) and place the eggs halfway into the moist material. When relocating the eggs, try your best to keep the eggs in the same orientation as far as which side is up. If the vermiculite dries out, you can add a little water to the vermiculite. But everything I've read says it's better not to moisten the eggs directly.
Good luck!
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MichaelB