From my understanding, since hair extensions are supposed to feel and look natural a human hair should be used unless you go for a cheaper alternative, that's when synthetic hair comes in.
There are salons offering this services and they have a ready human hair extensions ready for use which they have bought from the suppliers. You don't necessarily need to ask around for hair donors. But should you know someone with long hair and she's ready for a bob cut, then you can ask her if you can have her hair. Their are salons accepting and processing human hair into wigs and perhaps hair extensions too.
Hair Shaft ( The last time I checked, their salon is located in Podium Mall in Manadaluyong)offers hair extensions and they really are careful doing it so as to avoid damages to the existing hair.