I mostly 99% of the time shoot moonclips in a S&W 625 but sometimes shoot a S&W model 66 with speedloaders. https://www.midwayusa.com/product/3...67-68-taurus-66-669-689-38-special-357-magnum That is the one I use and most every one else uses, they have a shorter one that is good for concealed carry but this is the one for competition.
Can't help with the holders but the ones I use are not Safariland, just looked at them and could not find a brand name. The Safariland "333" will not work because IDPA rules place two speedloaders in front of the holster and one either behind the holster or on the off side. Safariland does make a single holder similar to what I use for moon clips, but I have never used them so won't recommend one way or another. https://www.midwayusa.com/product/5...-medium-and-large-frame-revolvers-epoxy-black
Sorry I can't be more help but try shooting revolver and it is addicting. Not a huge number of us but I keep seeing more people trying it and liking it.
I checked your profile and don't see where you are located. I am over in Illinois but shoot IDPA at Atlanta Conservation Club and Wildcat Valley Rifle and Pistol Club. If you are close to either and want to try my set up let me know and I can bring everything you need except the gun and ammo. Jim.