The easiest way to farm these would be by going to Western altepa desert. There's a bunch of manticores outside the zone line of kuftal tunnel. You can pretty much solo them 60+ with no downtime.
The droprate isn't too bad either. With TH1 I was scoring around a 1/3 droprate, and these really start to add up. If you ever do farm these. I recommend that you have 60+ inventory space and have mules in jeuno to sell them.
These sell INCREDIBLY fast, because they're used in the BLM JSE and also in ninja tools. You could literally put them on the AH walk to your MH and see them already sold. If you wish to profit more from this you can level clothcraft.
A Nice Bonus for doing FoV pages in Cape Teriggan. Along with these you can also get Manticore Hides/Fangs and Cockitrace Meat/Skins. As well as some ok exp. If you can solo them. Put that in combination with The Caskets and FoV Gil Bonus and your basically earring gil to merit. Slowly of course.
Desert Manticore
From FFXIclopedia, the free Final Fantasy XI encyclopedia
Job: Warrior
Family: Manticores
Crystal: Wind
Weak to: Water
Strong to: Fire, Wind
As Yuudye's TH *** on these drops I can say he's not lying. It's just a shame the market has become so flooded lately that selling hairs is like pulling them, painful.
I'm looking forward to the day I can sell off my back stock of hairs for a price I can agree with.