Two logical examples are Elven/Fey magical items:
- Boots of Elvenkind (DMG p. 155)
- Cloak of Elvenkind (DMG p. 158)
Ordinarily, magic items are not for sale.
Most magic items are so rare that they aren't available for purchase (DMG p. 135)
The DMG also points to them being possibly for sale but very hard to find for sale. (DMG p. 136)
In your campaign, magic items might be prevalent that adventurers can
buy and sell them with some effort. Magic items might be for sale in
bazaars or auction houses in fantastical locations, such as the City
of Brass, the planar metropolis of Sigil ...
The Feywild fits that general case pretty well, and has the reputation as a more magical place than the human world. Shopping there would be one way to suggest more likely access. The price, however, may be steep.
Any number of rings or amulets might be available, if the DM so chooses, but at least there is a basis for suggesting why and what. Page 135 of the DMG has some suggestions on what rarity of magic item fits the character level of the party/PC and price ranges, in the "Magic Item Rarity" table.
Work with your DM when using that as a reference.
Other items that fit the Fey theme
Some magic items are more chaotic and whimsical in nature: the Bag of Tricks (DMG p. 154), Bag of Beans (DMG p. 152), and the Wand of Wonder (DMG p. 212).
At the higher end, a Moonblade (legendary, DMG p. 216) fits into the elven or Fey theme.
Each of the items mentioned has a thematic fit with the Feywild as described on p. 49 of the DMG:
... a land of soft lights and wonder, a place of music and death ...
inhabited by sylvan creatures such as elves, dryads, satyrs, pixies,
and sprites ...