There are other revolvers that use similar systems (the ones that don't use shells). Dunno how well these drop-in replacements work, based on reviews it only works in Double Action though. But honestly I find it defeats the purpose of a revolver the same way a bolt action machinegun would.
You may want to check if your shells are compatible with any real steel speedloaders.
Review here:
http://www.airsoftretreat.com/features/reviews/hfc357/