I've known clients to use Alibaba as a good place to start. A quick search on Alibaba for "drinkware" will yield the following results for you.
Are you looking for a vendor to drop ship or wanting to buy in bulk?
I know for a fact that some vendors through Alibaba, you can haggle the price down a bit and even work closely without offline.
Hi Jason - Thank you.
I'm looking for a vendor where we can customize, dropship / and white label. I've found a few but they are not with Shopify. Was curious if were any already with Shopify. Otherwise, I can just do manual orders. Alibaba could work but I'm looking to make customizations for sure.