Ok so here's my problem...I just did a trade and got a M85np (AR mag), the previous owner stuck a MI quad rail on it. I can't stand quad rails and hate the weight it adds to this gun so I took it off in favor of the manticore renegade. But the problem I'm having is that the gun no longer has the front retainer (I guess it's called?) for the lower handguard which is quite important for installing this manticore. So my question...what do I do? Is there one I can buy? Or can I use one that bolts on maybe? I know they make some bolt on ones for Saigas but not sure if those will work or not. Thanks!

The bolt on may or may not work

APEX gets them from time to time. The FSB will have to come off,  which isn't a huge deal.  You should be able to knock it off with a plastic dead blow after removing the pins.