Instead of a museum retrospective that ends with a lavish pop-up gift shop, why not turn the gift shop into the exhibit?

That’s basically what the Whitney’s doing. For its new show, “Eckhaus Latta: Possessed,” the friendly, jeans-clad staffers — called “performers” — will retrieve works hanging from the wall for visitors who want a closer look.

Not only that, but you can touch, try on and buy the screen-printed T-shirts, hand-painted linen suits and intricately woven garbage-bag skirts that the young avant-garde designers Mike Eckhaus and Zoe Latta made specifically for the exhibit, on the Whitney’s free, first-floor gallery through Oct. 8. The limited-edition merch ranges from $60 T-shirts to about $7,000 for a Technicolor, plastic shirt that took Latta 800 hours to weave together.

Even the changing-room curtains, mirrors and hangers are museum-worthy — done as they are by the designers’ artist friends, such as Whitney Biennial alum Susan Cianciolo.

“The best museums give us the chance to step outside of the everyday and think about something — like shopping for a T-shirt — anew,” the Whitney show’s co-curator Lauri Freedman tells The Post.

“We didn’t know what the show was going to be, but when we approached Mike and Zoe 2 ¹/₂ years ago, we had faith they were going to be the stewards of something that was not only expressive of their practice, but also worth looking at and considering,” Freedman says. “I think this show does a really wonderful job of taking all of that and putting it in a context that feels very smart and really generous.”

The Whitney is hardly the first to blur the lines between art and commerce. Some of the city’s most fashion-forward brands have turned their stores into mini art meccas.

Here are four shops that could double as museums — and admission is free!

Louis Vuitton

(1 E. 57th St.)

The storied luxury-goods company has collaborated with artists on special-edition handbags for more than a decade, starting with a “Graffiti” collection from designer Stephen Sprouse in 2001. Its five-story Fifth Avenue flagship has a bevy of original artworks, selected by interior designer Peter Marino. A cheerful cartoon flower sculpture by Japanese artist Yayoi Kusama — who created polka-dot purses for Vuitton in 2012 — greets visitors as they enter the airy space. Also on display are gems from abstract midcentury painter Betty Parsons, mind-bending fotog Todd Eberle and sculptor Jeff Koons, who contributed one of his burnished balloon bunnies.

Agnès B.

(50 Howard St.)

The French designer’s Soho boutique also functions as a bona fide art gallery, with four to six shows a year chosen by avid collector Agnès herself. Past exhibits have featured 1970s downtown diva Maripol, experimental filmmaker Jonas Mekas and Malian portrait photographer Malick Sidibé. Agnès not only features her old artist friends, but new talent, too, such as Korean-American mixed-media artist Romon Kimin Yang, a k a Rostarr, who is currently showing his sketches — and selling specialty T-shirts — at the space.

Hayward House

(131 E. 70th St., second floor)

Luxe accessories designer Marin Hopper delved into her family’s robust art collection to decorate her intimate shop, located inside the Upper East Side’s Fortuny-wallpapered, Tiffany-accented Grosvenor Atterbury mansion. It helps that her parents are Dennis Hopper and Brooke Hayward, actors and collectors who hobnobbed with such art superstars as David Hockney and Roy Lichtenstein. In addition to paintings of Marin’s glamorous family members, the store is filled with treasures by Andy Warhol (one of his famed shoe illustrations), an expressionist painting by Jack Nicholson, and beautifully rendered, black-and-white portraits of Hollywood royalty shot by Dennis Hopper himself.

Cole Haan

(185 Greenwich St.)

To finish off its sleek, shiny new store at Westfield World Trade Center, the footwear company reached out to ArtStar founder Chrissy Crawford — who’s worked with brands such as J.Crew and Bonobos — to spruce up their spaces. Crawford selected pieces from her online art-dealer company’s collection that would complement Cole Haan’s urbane aesthetic. Look here for minimalist op-art by Bridget Riley, Ludwig Favre’s architectural photos of modern libraries in Paris, and a chalk-like doodle by Briggs Edward Solomon.