You don't need a bunch of alternate teaching materials to teach a student with a visual impairment. He will use most of the same materials that other preschoolers use, like finger paints, play doh, and blocks. There are easy ways to modify pictures and other learning materials. You can create raised lines on pictures with Elmer's glue. Simply squirt the glue and create shapes, letters, numbers, or whatever you like. When the glue dries you'll have a raised picture for the student to feel. This must be done in advance to allow adequate drying time.
Partially sighted children will benefit from large pictures and the use of sharply contrasting colors. Using learning materials of different textures can also be helpful and add variety. Letters and shapes cut from felt, sponges, or other materials with interesting texture are cheap and easy to make.