It looks like these clear vinyl products started being marketed in 1939. They made Elasti-Glass belts, suspenders, sock garters, neckties, watch straps, wallet inserts, pipe humidors, raincoats, and rain chaps.

Elasti-Glass
Reply
http://www.ebay.com/itm/271093599332
http://www.ebay.com/itm/281013674421
Chest: 23″
This ad campaign for Munsingwear ran 1939-1946. It was a pivotal time in the industry, as people switched from one piece knit or broadcloth union suits to the modern “streamlined” standard of briefs and boxers. Also notable is the introduction of t-shirts as a piece of outerwear, though at the time, it was reserved for casual and sporting contexts.