What can I buy for chicks to dust bathe in?

[BDutch]

This might be a dumb question but I’m new to chickens. I have 3 that are almost 9 weeks and a group of 10 3 week olds. The ground is covered in feet of snow. I usually give them some dirt but that’s not an option right now. What can I buy?

Only questions from trolls are dumb. And this is definitly a good question.
I have a big pot for plants in the coop. Under the roost and poop board. In the pot is a mixture of soil, playgroud sand and I put a few spoons diatom (diatomacious earth ) in to avoid/ terminate lice and other tiny bastards with a weak skin.
If the sand is very dry is doesn't freeze easily.