I've got this camera adaptor, the clamp inside diameter is 45mm and the height from the camera screw to the centreline is approx 40mm, was last used on an OM1 but I would think it would suit any camera with/ without a fixed lens.
The Barlow is a no-name brand 1 1/4" x2 in original box.
The adaptor $ 15, Barlow $20 delivered in Oz.
Drop me a PM.