Brownell's has them - pg 174 #084-000-006AB - $15.98/5. Ranch Products, a manufacturer of moonclips, was cheaper directly, but I haven't got a good number for them since they moved.
Now a caveat... if you have ever fired and fed a 625 moonclipped rounds - especially 230gr ball ammo - there is no comparison. The .45 ACPs literally 'jump' into the charge holes. The long, spindly spider legs of those loose .357M's dangling is hard to line-up all at once. The .45s spoiled me... I keep 140 such moonclips loaded. I doubt I'll get more 8-holer moonclips. YMMV.
Stainz
PS 8-hole moonclips are very case-manufacturer sensitive. I've found Starline to be the best.