Firstly--does anyone know the sizes of the dovetails?

Secondly, does anyone know of a sight off another gun that fits? I know some Ruger rear sights will fit some guns.

What I'm actually after is a front sight that will fit the dovetails and is fairly low-------as I'm intending to shoot with just the front sight. A broken front sight would probably do, but I'd be interested to know any other info as it would be handy for sorting out plinking guns fairly cheaply (hopefully).