EISCO High Quality Glass Lenses, Set of Four, Double Convex & Concave Lenses of Dia. 50 mm, Polished, High Quality : Amazon.in: Industrial & Scientific
FUN + LEARN Premium Optical Glass Double Concave and Convex Lens for DIY Experiments (50mm Pack of 2) : Amazon.in: Industrial & Scientific
ARGLabs Concave and Convex Lens (3-inch/75mm) with Wooden Stand (Brown, Big) : Amazon.in: Industrial & Scientific