While many folks feel moon clips are a drawback,, (and I used to be one of them,) they aren't actually. In fact, for a wheelgun,, they are quite fast. And you don't have to be a competition shooter to enjoy the benefits of having spare ammo quickly for a DA handgun.
I USED to feel it was a PIA,, until I got my first DA that used moons. Actually, it was a Ruger Speed-Six in 9mm,, that ONLY had 1/2 moons.
Later,, I found a supply of full moons. Then along came a few more guns that use moons. I have a S&W 45 acp, and a S&W 40. Now I have added a GP-100 in 10mm/40 as well.
And for those who feel moon clipped type of handguns need to realize there is a whole world of folks out there who enjoy them. ICORE competition is a hot place for them. And yes,, there are a LOT of folks who do enjoy the competition. Then IDPA, USPSA & others use DA revolvers as well.
And as for availability of clips,, TK Products, Ranch products are but a few places that sell moon clips for many guns.
So,, for usage & fun, they are NICE!
And for competitions,, they rule the game because they are fast to reload.
And ONE of the reasons they aren't always easily available is that folks who buy them,, usually KEEP them. And many of those same folks are NOT into competition.
So,, if a SP-101 in 9mm attracts you,, by all means,,, go for it. None of my DA's that use moons are for sale!