Small LiPo Supplier Suggestions

[technically_not]

I'm developing a small wearable project for a client that expects to produce the low thousands each year. The product needs to contain a small pouch-style LiPo battery, in the order of 200mAh or so, and it may need to be a custom size or at least a custom connection.

This must be a fairly common requirement, but I have no idea where to source these and my google-fu has failed me thus far.

Ideally I'd like a UK-based company that we can deal with, but I'm also open to considering a Chinese supplier as long as I've got a recommendation.

Any suggestions/experience/recommendations?