Battery for Arduino powered wearable (ATTiny)

Hey,

I'm working on a wearable device with an ATTiny.
Where is a good place to look for a LiPo or Li-ion battery that I can have access to lots of sizes and capacities?
Sites as aliexpress are not that good to look for, lots of duplicated products, can't look for specific size and some products are not related with the search.

Thanks.