A touch of vintage in Badstuestræde 12 has some nice stuff for men from various decades. They did tell me however that they wouldn't replenish the stock. The Danish men today are just too large to fit most of the clothes from back then so they were going to start selling mens wear reproductions instead. They said they would still keep their current stock though so there ought to be some left in April.

https://atouchofvintage.dk

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I use Poshmark and eBay for a lot of business casual stuff. More on reddit.com

Honestly you’re going to have your best luck searching on Etsy under the era you’re interested in and the term “menswear” and going from there. There are way too many sellers out there for anyone to provide you with a comprehensive list of them; particularly given that no one knows your exact tastes and the exact aesthetic you’re looking for. You might also find yourself branching into the aesthetic of overlapping eras; the forties, the sixties, and even portions of the thirties all have pieces that could be mixed and matched for a cohesive look. It depends on your personal tastes. Frankly, there’s no easy or cheap way to completely source a vintage wardrobe. You’re going to have to be willing to peruse pages of Etsy, EBay, Facebook marketplace, and even estate sales. You have to be patient, you have to look for quality, and often you will have to pay for quality. Things that are true vintage and in good to excellent condition will not be cheap simply because they are not easily sourced and they have aesthetic and historical value. If price is a concern to you my suggestion would be starting with some vintage reproduction like Some Like It Holy. They are still priced higher than your average target or mall clothing but they are certain to last you longer than true vintage clothing you will pay a comparable price for and not have the familiarity of upkeep with, for example. Overall, I think you need to do some research about your preferred aesthetic and places that cater to that aesthetic from both a modern reproduction and true vintage standpoint. Browse Etsy, browse eBay, browse Poshmark, hit up estate sales, and start familiarizing yourself with what to look for, how to care for and store vintage clothing, and go from there. It’s not a quick process. It’s slow sourcing and it takes a lot of time and a keen eye to become adept at this time of purchasing and the proper care of those purchases. More on reddit.com

At the moment for menswear it's probably Depop.

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