有小一点的吗？

You use this when you are holding an object. Or when you are looking at a menu. Just point at the item and say the phrase. You can add 请问 (may I ask) at the start to be extra polite. It works for clothes, shoes, bags, and even fruit at a market. If a shirt is too baggy, this is your line.

Use it in any retail environment. It is perfect for the night markets in Taipei. Use it in a high-end mall in Shanghai. It also works for food portions if you aren't very hungry. If a waiter brings a giant plate, you can ask this. It shows you are practical and know what you want.

Don't use this when talking about people's physical stature. That would be quite rude! Also, avoid using it for abstract concepts like 'problems' or 'ideas.' It is mostly for physical objects you can touch. Don't use it if you are trying to negotiate a price. For that, you need different words for 'cheaper.'

Chinese shopping culture is very interactive. Sellers expect you to ask questions. They often keep different sizes in the back or under the counter. Asking for a 'smaller one' is a standard part of the 'shopping dance.' In many local markets, items aren't always displayed by size. You have to ask to see the full range.

You might hear 有没有小一点的? which means the exact same thing. It just uses the 'have-not-have' grammar style. If you want something bigger, just swap 小 (small) for 大 (big). Then you get 有大一点的吗? It is like a Lego set—just swap the adjective and you are ready to go!