Go to Walmart, or any store with a decent gardening area....and get some of those plastic saucers that go underneath flower pots. They look like they're the terracota sort, but they're just plastic. They make perfect hides, and cost only pennies. Just cut or melt an entrance hole in the side and flip it upside down and there ya go.
Really, any solid color plastic container will do...just make sure it's small enough to fit snugly around your snake when it curls up inside. They really like tight, small hides and it's almost impossible to have a hide that is "too small" for these guys.
And yes....they'll move 'em around and rearrange the "furniture" in their enclosure. It's not a big deal and nothing you need to worry about.