I will try to answer your question. I taught revolvers in LE for many years. HKS speed loaders were always the most durable and reliable in my experience. Some of the others may be a little faster for competition but HKS is what I would buy if it was my money. Hope this helps.
For "speed-loaders" (spell it anyway you want), I typically think of the cylindrical style, not a "speed strip".
For an 8-round .357 S&W, this leaves only the 5-Star brand. Using Post#2's website reference, here's a link: http://www.pistoleer.com/5star/speedloaders/357/
I have this brand for my S&W 627Pro and it works well.
I'll often carry an 8-round speed-strip, but that's a personal choice and doesn't reload as quickly as a speed-loader.
I've tried the "Maxfire" brand in a 5-round version and didn't like the flexing, plus I couldn't just put one in a pocket without the rounds pulling/falling out of the speed-loader.
For Post#4, so far, I'm unaware of HKS making an 8-rounder for the subject gun.