https://www.fraingroup.com - likely good place to start.

Also setup Google Alerts to scrape Craigslist + email you immediately when something shows up you're looking for.

Happy to share some insight - hope it’s not too late seeing as this question was posted a while ago.

I don’t know of any good suppliers at the moment, but I do know how to find them. It’s not as complex as you might think...

If you are going to spend less than $1,000, then:
1. Search Amazon for available products and suppliers.
2. Search Google for available products and suppliers.
3. Search Thomasnet.com for available products and suppliers.
4. Ask a local convenient store owners who they use for a supplier or if you can buy equipment from the owner.

If you are going to spend more than $1,000, then you may want to consider issuing a formal Request for Quotation (RFQ). This will allow you to compare multiple bids by not only price, but other factors as well such as delivery charges, quality, customer service, etc.

If you need more help, feel free to reach out to me.
Best regards,
Brian

For plastic cups and other supplies I would go and ask several bubble tea shops where do they get them from. There is no better info than straight from your competition.
On the machine, you should probably try to rent first before to see if the business has legs before you commit to invest the money. Just saying so you don’t get your money stuck on an asset you can’t get rid off later

One additional online source you may want to consider is Panjiva. Panjiva is an online source that has created and maintains a database of commodity based and specialized supply information on companies and other agents engaged in international trade. You can receive timely insights on companies at every stage of the supply chain. From manufacturers and buyers to shipping and logistics.