Fill and spill containers are easy enough to come by around the house. An empty baby snack container or other food storage container with a lid, or even a plastic bowl or cup works just great. Experiment with different containers.
You an fill the containers with just about anything. We've found that all those lots-of-links we have laying around the house, or clean baby food jar lids seem to work best. They are "small" objects, but not so small that they are a choking hazard. The baby jar lids are great, not only because they're free, but also they make a nice clanking noise. The lids sound even better when used in an old baby snack container with a metal bottom!!
Try not only filling and spilling, but moving the items from one container to another!