How about Rudi Gernreich's topless bathing suit, introduced in the 1960s? The prototype I saw was like a one-piece maillot made of a stretchy material but cut off just below the bosom and held up by a one spaghetti strap that went around the neck. On some beaches in Europe some women did start going topless some time during the 60s or 70s, but I don't think there were more than a handful of the topless suits sold.

Then there were the paper dress and the paper underpants, which were also introduced in the early 1960s and never really became big sellers.