I doubt very much that anything like that exists. A pad hack is probably your best bet. That being said what your trying to do may simply not be possible depending on how the console versions of the games you are trying to play work with a controller.
Both the PS2 version of Silent Scope and HOD4 on the PS3 work with analog controls and all analog controllers use a pair of pots for each stick, same as positional arcade guns. If I have a way of connecting the pots, it will work.
The only part I am not sure about is if I will be able to satisfactorily calibrate them. On a Windows PC there is a calibration option so you can make sure the gun aim roughly matches the on-screen crosshairs. I am not sure any such options exist on these consoles.
I think the scope will be easy to hook up as the scope view on screen moves moves around with the crosshairs so pointing a camera at it will be easy if I can calibrate the gun. But, that's academic until I have a way of connecting the pots.