I built a 3-chime unit using two different brands of doorbells purchased on Amazon for under $40, total. A few pieces of scrap wood and some miscellaneous hardware are all that are required. This is a pretty easy weekend project that greatly enhances your table if you play EM games. Note: This assumes you already have DOF running and have driver hardware for toys and this is just an additional toy to be connected and configured.
Below is a 26-page pdf file with instructions (lots of photos) and a video of the chime unit in operation so you can see and hear it prior to deciding to build one for yourself.
Instructions: DIY Chime Unit.pdf