For the silencers, AirsoftParts.ca has them and a good selection.
But, the way I see the rifle, the silencer needs to be beefier. The skinny silencer would look off. I like the look or the TRX 7" rail honestly, and from pictures it looks like you could fit a silencer like you described easily. The bigger silencer might not fit, but it could be worth a shot.
Unfortunately for me, the project is postponed because I spent too much, and my girl is not happy