HOWTO make an 8-track cassette walkman

Here's an "admittedly mad" Instructables project from XenonJohn: how to hack a portable 8-track tape walkman in the style of the original Sony cassette Walkman.

This is an admittedly mad project to see what might have happened if Sony had invented the Walkman earlier than they did – and made it so it took 8 track tape cartridges (which came before cassette tapes were invented).

In other words, can I make a personal 8 track player with just headphones in the style of a Walkman?
How small can I make it? Bear in mind it needs quite a bit of power to move the tape loop around inside the cartridge.

8 Track Walkman-Pod thing (Retro-tech)

(Thanks, Michael Chabon!)