I got them from G-10, Islamabad for ~Rs. 2500/- pair. They are very reliable, but just make sure to inspect axle on weekly basis and replace axle boots as soon as you wrinkles/minor cracks on them while stretched (when wheel are turned) and always use 90gm CVJ grease in them. You will get grease with new CVJ so use that.
Sherry axle kit with Nippon axle boots is best combination for 2-3 years. Always get Nippon Axle boots.
I don't know about Karachi, but contact here 03002116069, IIRC It's Afzal from Hameed and Sons in Karachi, recommended suspension shop by many Pakwheelers. Visit them and they will guide you best.
The key to long lasting axles is, replacing axle boots at the point when they are about to tear, i.e when they have wrinkles/cracks upon stretching (when wheels are turned).