You could use Arisaka parts like the body, and a scout clamp style rail mount is easy to find. You'll need the UE07 tailcap and a SF ST07 too. All are readily available but why not just put a WTB ad here on CPF? By the time you buy a 2 cell body, a UE07 tailcap and the pressure switch, then the mount, you will probably be into it for what you could have purchased one already assembled. BTW welcome to CPF!
