Sorry; reading back I realised I answered the wrong question, or indeed one that wasn't asked lol
Some of the non/off brand stuff that comes from China doesn't have UPC codes and this can be an issue for selling on Amazon. I'd check with the dropshipper for the exact product name/brand and check the databases above just in case they have an entry for it; failing that, you can buy codes from places like MyIdentifiers.com (which is who Amazon recommends on their UPC page) or (way cheaper in the long run) register with GS1US.org and create your own in bulk(expensive up front cost but much much cheaper than buying them individually from brokers.)