This is what I personally use on my KWA M4; https://danieldefense.com/mounts/sling/ez-carbine-qd-swivel-attachment-point.html A little on the expensive but when it comes to Daniel defense you definitely get what you pay for. *If you buy that you will have to get a QD (Quick Detach) sling swivel (push button type) if you haven't already* If that doesn't work with the buffer tube and/or doesn't work with your budget, you can try getting a 2 point sling that goes around the handguard and stock, slightly uncomfortable in my opinion but you have to do what you have to do. Hope this helped, Goodluck.