David & Amaya High-Density Foam Mattress Extender – Sofa Bed Gap Filler, Rectangular Bolster Support Pillow, Armrest or Headboard Cushion Foam Only (Blue, 120x20x10cm)

This product would be an excellent choice for those looking to extend and maintain the comfort of their sofa bed by adding extra padding and support under the mattress, particularly in large living rooms or open-plan spaces with plenty of floor space.