I want to buy a gift for a friend and I'm looking for a one volume licensed manga. Buying a whole series is too expensive, so I wanted to buy a short one volume manga, but I've searched and can't seem to find anything. Any suggestions would be helpful

If your friend is okay with horror and you're willing to pay $22, there's an omnibus of Another.

Here's the amazon link.

"Wanted" from VIZ if said friend is into generic pirate shoujo. Otherwise, there is a bunch of Tezuka Osamu series from Vertical that I'm pretty sure are only 1 volume.

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Solanin
Pink (OKAZAKI Kyoko)
In Clothes Called Fat
Tekkon Kinkreet
Garden Dreams
Ohikkoshi
Utsubora
Helter Skelter
A Drunken Dream
Tropic of the Sea
Sakuran
Black Bard
The Strange Tale of Panorama Island

Here are some that I know of. I tried to include some variety so there are different genres and some newer and older works. Also, don't forget to check the websites of various publishers, big and small, since there's plenty more.

Hope this helps.

Olympos *omnibus
Elhanburg no Tenshi this one will be released in the spring

There are some one shot collections
Time Killers
Beautiful People
ic in a sunflower

And there are some 2 volume series like
Rabbit Doubt *omnibus
Kieli
Gyo

Any genre you want specifically?