My day job is building one-off prototypes as a mechanical engineer in a research lab, so I end up sourcing a lot of random stuff like this in small quantities.

As others have mentioned, my first stop is the usual suspects, mostly McMaster and Misumi. If not I might check with a few local industrial distributors, including some independent ones but also local branches of Motion Canada, Wajax, GBS and whatnot.

If that fails, I usually resort to contacting the manufacturer directly, either phone or email, and asking if they either do B2B direct sales or if they have a distributor for my region they can put me in touch with.

Industrial sales is still very much old-school b2b, around here at least (Canada). For many of my local suppliers, the only way to get an idea of prices is to call or email a RFQ and wait a day or two to get a quote back. One lists their prices in their paper catalog only, which at least saves me the RFQ quote.

Many distributors are B2B only but some, especially in my small-ish town, will do B2C too.

The first stop for things like this is McMaster-Carr, but they don’t seem to carry this variety of rivet nut. So one must resort to desperate measures: the manufacturer sells them in quantity 50 on their website.

https://eshop.boellhoff.de/en/Riveting-technology/RIVKLE-Bli...

These are cool indeed, the closest I'm familiar with that are standard at local hardware supply stores are Concrete Anchor Bolts.

They stick up however many inches and can be a tripping hazard, and are a pain to angle grind out if you ever need to remove them.

I wish these self-seating rivet nuts were widely available! It seems like a no brainer.

Amazon and Aliexpress are a good source for specialty tools that are unavailable in local retail stores or have an excessive markup.

As the other commenter noted, mcmaster is my first stop, after that MSC, grainger, fastenal, hi strength fastener, etc.