Bra

A bra or brassiere is an undergarment worn mostly by females, which in medieval times consisted of nothing more than a well-constructed leather strap. In mainstream Smurfs media, this would appear mostly in the form of a swimsuit top that Smurfette would wear, although she would usually appear in a one-piece swimsuit.

Empath: The Luckiest Smurf stories
In the EMPATH: The Luckiest Smurf story series, due to Smurfette's physical appearance being different from her mainstream appearance, the bra would also appear in the same manner, mostly as part of a swimsuit.

The Smurfettes on Smurfette Island wear a crop top bra as part of their normal dress. Sassette during her brief time as an adult Smurf would also wear a crop top with her overalls.

Hefty had to wear a crop top while he was being tormented by Ghinelle the genie who partially transformed him into a female Smurf.

Smurfy Tales
In Smurfy Tales, Smurfette begins wearing a bra after "Changes". She generally disaproves at first, but the grows to accept it.

Hero: The Guardian Smurf stories
After the events of the story "Smurfette's Crazy Love", Smurfette now wears a bra as part of her everyday dress. Wonder soon begins to wear a bra, after being given plastic smurfery by Papa Smurf.

Smurfs Abound series
Smurfette's bra was shown in Clumsy's Mistake after Clumsy accidentally rips her dress.

RDK Stories
Although no female is asked to reveal or speaks openly about their undergarments, Falla and Savina both wear bras constructed of strapped leather bindings sewn together with duoble-hex threading, allowing both mobility and secure fastening.

As for the Smurfs, Smurfette and Moxette do not require a bra because they do not have developed mammories and are not set to have any until they are ready to become mothers (if they do decide upon this).

Traction stories
Smurfette does not appear to wear a bra in these stories.