So... I decided I wanted one of the NPCs in my new 5e campaign to have a girdle of masculinity/femininity. She's a tiefling cleric of Sharess who is also a festhall madam (which is not an unusual occupation for a cleric of Sharess) and has hired the party to escort her from Silverymoon to Waterdeep and back as she recruits workers and buys furnishings for a new festhall in Silverymoon. I thought it would be fun for her to be a potential romantic interest for anyone in the party, so it seemed like a good idea to give her a magic item that allowed her to switch sexes as needed.
I'm well-aware that the girdle was a cursed item back in the AD&D era -- switching the character's sex against their will and not allowing a change back without the intervention of a god -- but Blog of Holding had an awesome idea about allowing PCs to "tame" cursed items rather than simply discarding them after a remove curse spell. This seemed like a good way to redeem the girdle; I thought it would involve something like Hercules' enslavement to Queen Omphale where the character could choose to embrace the sex change, learn to live as the other sex, and then earn the right to change back (after which the girdle would allow for fluid changing between sexes).
And then I realized that such an idea was still based around the offensive ideas that changing sexes is a curse and that cultural gender roles are inherently linked to biological sexes. So I decided to just make a new magic item.
Belt of Transition
Wondrous item, rare (requires attunement)
This belt has 3 charges, and it regains 1d3 expended charges at dawn. When you don the belt, you may expend one charge to switch to another of your race’s biological sexes, to an intersex form combining aspects of your race's sexes, or to a sexless form. Using the belt to disguise yourself as a different sex gives you advantage on any relevant ability checks. You return to your original sex when you doff the belt.*
*Originally "Common in the enlightened eons of the ancient magical empires, but rare in this decadent days, the belt of transition allows you to switch between your species' biological sexes at will or assume a hermaphroditic form combining your races' sexes. Using the belt to enact a disguise gives you advantage on any relevant ability checks."