Here is another set of small containers which are perfect for holding sets for adding and subtracting.
These are currently at Walgreens for $1.50 for a set of 3.
Each container opens up and stores tiny manipulatives.
I put small, flat glass stones in them, but you can put two-sided fun foam pieces or any other tiny counters. Just make sure that each student has the same number of pieces. In a small group, they can add to that sum or subtract from it and record their results by writing a number sentence.