"A-Zoom - Precision Snap Caps" -
http://www.azoomsnapcaps.com/home/
As I posted earlier I don't use snap caps.
I've handloaded my own 9mm dummy rounds but they've never held up. In my experience the bullet falls out of the case with extensive use. As a result I don't trust handloaded dummy cartridges, especially for training to clear stoppages when I'm also shooting live ammo, which is why I use ST Pro Action Safety Dummy Cartridges.