What is the name of this AC plug, and do they still exist?
Assuming by "Type I" you mean the australian plug IIRC they are no longer allowed to be sold as separate plugs to the general public (apparently there were problems with people making up cords with the stackable plugs on both ends), but are apparently still available for professional use and are certainly still available as part of ready-made extension leads.



From some further searching it seems the term is "piggy back". Googling "australian piggyback plugs" finds a few results, including a claim from Schnider electric (who bought out clipsal) that they are still available but only to OEM customers with a minimum order of 100 units.

One of the other results from that google search mentions a part number "PDL 940 CL", removing the "CL" (which appears to be a color identifier) from that part number and googling "PDL 940" turns up a couple of suppliers, they seem fairly pricey though.