When I don't have many objects that start with our letter of the week, I have found that a sensory tub with water beads is a good way to go. The water beads are so much fun in and of themselves that they don't need too many things added to them. I collected Trip's dinosaurs, dog, a few ducks, and some foam Ds to add to the orange water beads we used for our Halloween tub.
Trip especially enjoyed the dinosaurs (which he calls "dinafriends" for some reason). They had to fight,