It's possible, but not from the factory.. I have the TRR8 in .357mag -- great gun, but I've never bought a tool to load the moon clips.. don't see it being worth it at this point in time.
If you have ever used moonclips I think you would find that they are substantially faster than a speed loader, Looks like I'm going to have to have another of my current ones sent to the gunsmith
Wife bought a .44MAG with speed loaders to carry around the farm. She seems to like it... Also, she can quickly re-load and be ready to fire again as fast as she can drop and load a clip. A .44MAG will definitely ruin someone's day worse than a 9mm ;-)