A properly formed plectrum is a three dimensional object that cannot be punched out of a flat sheet without additional finishing that requires the hand of a master craftsman.

And, as previously noted, the credit cards in the display ad are nearly always laminated with at least a "surface coat" that frays and splinters if punched or cut with scissors/shears - or used for plecting.

Plectra can be "custom made" by the sufficiently skilled artisan, but the mass-marketed ones fit to use now are most commonly made by injection molding in a very expensive machine built by a skilled toolmaker, using properly formulated molding materials compounded by knowledgeable chemists.

The toolmaker is from the "Hang" family and the chemist's name is "Wong."

You can probably find a nearly identical punch at "Hobby Lobby" or "JoAnn Fabrics," made and sold so that "creative little old ladies" can produce their personally unique works of art by punching out little shapes identical to the ones everybody else punches out and pasting them into their scrapbooks (the same ones everybody else bought at the same stores) according to the same detailed patterns that everybody else follows.

When the LoLs get done they're entitled to call themselves "artists," but if you use the punches to make plectra you're still "just another whanger."

John