You seem to have a good feel for the idea that buying through a reputable distributor like Adafruit is paying for ad-hoc quality control. They very likely are buying from a range of different factories and then certifying that the item in question (pump) hits their specified needs. They might have looser needs than you do.
When I move outside that realm for my own product needs, I do two things:
- Start slow
- Build relationships
By start slow, I mean I will sample a few products at a time, instead of buying the entire amount for my project. So if I need 100 pumps for an upcoming design, I will only buy 1 or 2 but from a wide range of suppliers. Then it’s important to set up criteria for incoming testing. The nice thing about having that rigor is you can do easier comparisons (if not time consuming), and also use that same test criteria to test future pumps, should you need to find a new supplier. This is what large engineering and manfuacturing companies do as well.
For building relationships, it’s important to start from the beginning. One example I have is I was trying to source an odd cable from a range of suppliers on Alibaba. I worked within the Alibaba communication system and had to keep up with the 3 or 4 that I engaged at the beginning of the process and keep communicating my needs as we moved towards production. They will be eager to win your business and sometimes a bit…persistent. At the beginning, I am always careful to mention that I will be happy to pay for samples and shipping. I am very careful to also be honest with quantities. I am surprised that many factories in China will still service low quantity needs, as many of them are set up for that (locally they service small orders) and they also want to offer other services and win future business. So from that perspective, it’s a symbiotic relationship. I have found the agents on the other end of the chat to be very pleasant. On the Amazon side of things, it’s much less relationship based, so if you think you will have custom needs, I would maybe go more towards a marketplace solution like Alibaba.
Please let us know about your experience as you try these things out!