You don't say which Speed you have but if it's an Anniversary or earlier, lens boards are easy to make up from any number of materials. My favorite is masonite, but foam-core board in black has served me well on a number of occasions. Just cut them 4x4 and chamfer the bottom edge on the back so as to fit into the slot more easily. Draw lines from corner to corner to mark the center and cut out the hole to size. Usually talkes me about 15 minutes to make a "Q&D" board (quick and dirty construction).