Rail to fit underneath M203 heat shield on M16

[Majestyk]

I have thought of trying to recreate the MW2019 "Stock M16 Grenadier" barrel assembly. I was convicned that the lower section fo the M5 RAS will fit however it turns out it does not due to the heat shield bending inwards at the half part of the shield which means it's short couple of mm's to fit inside perfectly. I have come across somebody else with the same idea and they ended up cutting up the rail to make it more slim. I have looked around the interent at different rails to see if they would perhaps be slightly slimmer but it looks like they are all the same size to fit perfectly in the delta ring and the retainer at the front sight. My question is if there is an actuall slimer rail that would attacht like the M5 RAS & other drop in rails. Perhaps there's a better way to just mount a rail section which I have not thought of? I've attached the pictures from somebody that has completed the build.

[TheFull9]

Interesting idea, but I'd say there's not much chance you'll find anything of reasonable price to just drop in; I've never seen anything anyway.  I think there are some RS aftermarket handguards which mount to the barrel nut in the classic military M16 fashion and have skinny 6 o/clock sections but they aren't cheap (look at some of the offerings from Midwest Industries), especially since you're just not using 75% of said handguard you've bought.  This is going to be a dremel/hacksaw/file job, but if you don't have those tools they're cheap to get and simple to use and the process won't be hard, you just hack chunks out of the sides as per the pic.