disposal stores near central or in haymarket have surplus ww2/post ww2 jackets, usually german.
dont get german though everyone has those
i bought a ww2 australian flying suit, cut the pants off at jacket length, sewed a hem and now i wear that. it's pretty close to the one in that video. fireproof too, bonus.
Australian army has these things called "battle smocks" (judging by the colour they're probably vietnam era or a bit earlier) which look like that one... but i doubt you'll find THAT jacket exactly.