Malcom,
You haven't said what scope you want to plug this into but looking at that extension in the image I'd guess an 8" newt.
After checking your links and looking around it appears they are trying to increase profits and are splitting the camera adapter from the nosepiece and selling them seperately.
I've attached pictures of my old canon adapter and you can see it splits into many pieces. When I was using it I unscrewed the tiny screws around the bottom part and removed that insert from the bottom section so the top tube screwed straight in. I was lucky that there was a thread inside to suit.
I believe this one is the best these days.