旅行袋(lǚ xíng dài) - travel bag, holdall in Mandarin

旅行袋 (lǚxíngdài) is a "travel bag" or "holdall", the soft, zip-up bag you sling over a shoulder for a short trip. 旅行 (lǚxíng) means "to travel, a journey" and 袋 (dài) means "bag, sack", so it is straightforwardly a "travel bag".

It sits between two other common bag words: 行李 (xínglǐ), "luggage", is the general, uncountable word for everything you're carrying, while 旅行袋 (lǚxíngdài) names one specific item, the soft holdall itself, as distinct from a rigid 行李箱 (xínglǐxiāng), "suitcase".

The measure word is 个 (gè): 一个旅行袋 (yí gè lǚxíngdài), "a travel bag". Pack it with 装 (zhuāng), "to load, to pack": 把衣服装进旅行袋 (bǎ yīfu zhuāng jìn lǚxíngdài), "pack the clothes into the travel bag".