well you can make your own when you get a nice lathe to do the bits on...there are a few places that carry the 30/25mm tube.
Or...why not try a HW95 with 23mm sleeve, so 85mm stroke 23mm piston have the cocking shoe push back on the piston skirt like on the LGV and make the piston rotate.
85mm stroke is 35CC or 80mm is 33CC (approx) plenty enough for 11fpe and the action has decent spring room