Yes, there are winter sleeping bags designed for side sleepers, often featuring a roomier cut or a special design that allows for more mobility. These bags typically have additional insulation in key areas to maintain warmth even when the sleeper shifts positions. Look for spoon shape and the modified mummy shape. The spoon shape offers a wider profile at the shoulders and knees for more freedom of movement, while the modified mummy shape is slightly roomier than traditional mummy bags, providing extra space without sacrificing too much warmth efficiency.