Moon clips are much less expensive ordered through Ranch Products, the company that makes most of them. The draw backs are they only sell by the 100 and you can't order through their web site. You have to call them and understand they're only a small family business. None the less they make all the moon clips S&W sells. IIRC 9mm SP101s use the same clips as S&W model 940s.
Ranch Products
PO Box 145
Malinta, Ohio USA 43535
Phone: 313-277-3118
I own a 940 and other S&W revolvers chambered for auto pistol cartridges. The effort required to remove their empties without clips is usually exaggerated. It's common for some or most of the empties to fall out just pointing the revolver up. The rest come out with the slightest tug with my finger nails. For 40 years I've been reading about people poking empties out of 1917 .45ACPs with a rod, but some how never seen it done in real life. At the worst reloading auto pistol cartridges without clips in a DA revolver is faster than a reloading a SA revolver.
There is one exception: relatively high pressure steel case cartridges in 9mm and .40 S&W. Don't even fire them in your DA revolvers. Steel cases do not contract back after expanding as much as brass cases do. Ejecting 5 9mms or 6 .40 S&Ws at a time takes more strength than DA ejector systems have. It just bends the ejector rod. I haven't tried steel case .45 ACP because they never were priced low enough to be tempting. At their lower pressure they might be O.K., or not.