I employ a rather 'dirty' method to this problem.
First i cut some aluminium sheet with a hacksaw, using an old board as a template, I then use a drill to make a circle of holes the size of the lens diameter. Hacksaw through the holes to make the circle, and use a file to smooth the edges ( or dremel etc ).
This is the dirty bit, place the lens through the hole, if the focal length permits it position the lens through to its mid point, or a point where it is balanced on the camera. Either side of the board position a jubillee clip, these often have large bolt housings on them - position the bolt housings opposite each other for stability. Tighten the clips so that the lens cannot move fore or aft. Then liberally cover with black tape, both to cover your hideous bodge and also to prevent light leaks.
This will work, you won't need the large flange - it's very cheap - SK Grimes will make a beautiful solution at an impressive price.