You can put them in soil at any time, even before they've rooted as they'll just root in he soil. If you can't find perlite make sure you use a very well draining potting mix. Don't use a potting mix marked water retentive or anything like that. If you can't find perlite I doubt that you'll be able to find vermiculite either. You can use builders sand and/or orchid mix to help with drainage. Do you have a Home Depot or Lowe's? If so they should carry perlite in the indoor plant dept. It might be worth your buying a big bag of perlite online. It's bulky but weighs very little so shipping shouldn't be outrageous.

Is there a Walmart near you? They usually have perlite around in the plant department. It's important to make sure the mix is light enough to allow the new roots to get through.