also: ウェストポーチ
noun
waist bag; belt bag; fanny pack; bum bag
A small bag worn around the waist, often with a belt or strap. In Japanese, this loanword is the standard term for what is called a fanny pack (US) or bum bag (UK).
from English waist pouch
旅行のときはウエストポーチが便利だ。
A waist bag is handy when traveling.
彼はいつもウエストポーチに財布とスマホを入
He always keeps his wallet and smartphone in his fanny pack.