I have one, not sure if they are still available although I doubt it. I also have another similar one that is an older, smaller rep. These are not tourbillons but rather 'open heart' designs with visible balance wheel under the dial window.
The ST-19 is a reliable movement although the winding stems are very thin and fragile. For the member with the broken one, a cheap cartel Daytona or various other rep with ST-19 could be bought to transplant parts to the Zenith. Or a replacement movement can be bought on Ebay, search for ST1902 there.