The Photoflex Adjustable Shoe Mount Connector for Small to Medium Litedome Softboxes accepts most shoe-mount flashes. It connects to a Photoflex, or Chimera Speed Ring, and allows use of that flash with a 12x16" softbox.
The Photoflex Extra Small LiteDome comes with a universal speed ring. This adapter connects to that, or any other Speed Ring.
Height of your flash is easily adjusted, and locked into place in the optimum position.