I need a Rear Sling mount

Hey ya'll how goes the airsoft war? Quick question...
I have a JG M4 S-System (got the enhanced gears verison) and I was wondering if there was anyway to put/make on a rear sling mount. There is a divot (small hole or whatever) near where the lower reciever meets the buffer tube. Now i'm fairly certian I could just push in a rear sling mount into the hole like this(http://www.airsoftgi.com/product_info.php?products_id=1518) ((the rail on the mount come off)) but I don't know for certain because my gun didn't come with any directions as to how to go about doing so and actually I think JG put rear sling mount is on the tip of the retractable stock (pretty dang useless if you ask me); and there is NO way i'm paying 30 bucks for some stupid 3 point sling so I could use some help.

Thanks for reading this and if you didn't, there is a 500FPS .43g Madbull sniper BB headed straight for your forehead...

"Who Dares, Wins."

This is what you're looking for i think.