For a tank style cage the duna multy might be good as well. It's slightly smaller than the Hamster Sky but he may settle better in a tank style if that's what he's used to. You can't fit an 11" wheel in it though - 10" possibly so it would need to be a 9" wheel for the wheel which means getting a new wheel too.
Cage Duna Multy | Welcome to Porton Garden Aquatic & Pets