Wheelchair trousers by Kitted Clothing.
These are made from a lovely thick fleece lined jersey, so are very comfortable and cozy, especially on cooler days. The waist line is at an angle so that children who are sitting all day don’t get a cold lower back from trousers sliding down. They’re also slightly longer to reach ankles even with bent knees.
These two are a gorgeous sunflower yellow and rich kingfisher blue, so they look as good as they feel.