I didn't feel like spending the $15 for a chalk bag so I'm spending too much time making this instead. It's used by holding it (or attaching it to a belt) with the stalk pointing down, so you can push it up to dispense a small amount of chalk, and then reset it by letting it go. Finely powdered chalk will dispense more at a time of course, but I still plan to increase the flow. With the stalk fully seated forward, it does a good job of keeping chalk contained.
I printed this using PETG, with 3 walls and 15% infill. The body and stalk print in place with a built-in support tower, but I still turned on build plate supports for the surrounding area. I'm currently using a spring with an 18.2 mm diameter, but the dimensions don't matter too much as long as its between 12.5-19 mm wide and long enough to push the stalk fully forward.
Overall Dimensions: 125 mm x 60 mm x 35 mm