small bag; small satchel
A small bag or satchel, typically used for carrying personal items. The kanji 小 (small) + 鞄 (bag) directly conveys the meaning.
She put her wallet and phone in a small bag.
A small satchel is handy for travel.
Compound of 小 (こ, 'small') + 鞄 (かばん, 'bag'). The reading こかばん is a straightforward combination of the readings of its components.