Stackable guest bed

I came across this idea in Google for a stackable guest bed.

http://www.connox.com/categories/furniture/bed/rolf-heide-stacking-bed-…
The above is the original designed in 1966.

Others are:

http://www.zeitraum-moebel.de/eng/produkt.php?Produkt=GUEST&Seite=1

and

http://pinebed.co.uk/page10.html

and

http://www.homedit.com/staple-bed-by-alexander-seifried/

and

http://www.connox.com/categories/furniture/bed/rolf-heide-stacking-bed-…

I'm in Australia and we have nothing like this available here so I would like to make one for my daughter’s room.

Does anyone know of any plans available or is able to suggest how to go about building one. I would like them to lock together similar to how bunk beds can (maybe with a metal rod). I would also like the top one to have a bed head if possible to stop the pillow from disappearing etc and to make it look more like a single bed but I like the idea of turning it into a double bed when guests visit such as her grandparents.

Any help and advice is very much appreciated.

Ang.