I would recommend looking for suits made with fabrics that have some natural stretch to them, such as wool blends or performance fabrics like polyester and spandex. These materials can provide both comfort and flexibility, making them great options for a stretch suit. Additionally, make sure to pay attention to the fit of the suit, as a well-fitted suit will also allow for more movement and comfort.
Another thing to consider when choosing a stretch suit is the occasion you'll be wearing it for. If it's for work or formal events, a classic wool blend suit with a subtle stretch will give you the perfect balance of comfort and professionalism. But if it's for more casual events, a performance fabric suit with a more noticeable stretch can provide both comfort and style. Just be sure to choose a fabric that's appropriate for the occasion and fits your personal style.