MD, a coupla points to think about. I have a Blackhawk that came with a 9mm conversion cylinder. Performance (velocity & accuracy) is very underwhelming. I played with it a few times when I first got the gun, but it has not been touched in the last 25 years.
Also, before you spend money on this, you might want to call them and find out if your gun will work properly without the moon clip. Basically they are going to machine .022 of the rear of your cylinder to make room for the clip. Im not a gunsmith, but it looks really sketchy to me. Where Im going with this is: If KT goes out of business and your last clip breaks you are out of business until you get a new cylinder fitted.
A buddy of mine has an old WW2 gun (S&W?) that uses moon clips. He says they are real pain to load & unload. The new ones might be easer, and they have all kinds of cool tools they will sell you, but give it careful thought. I think you would be better served to spend your money on a few standard speed loaders and a big box of .38 spl range ammo.
On the other hand, you would have something on the range nobody else has and thats always a lot of fun.