After you do your research and finally decide on which vendor to go please, for the love of god, buy them from the main / official retailer - there have been thousands of users that ended up with their funds stolen because they either got them from Ebay (shady sources) or from some Amazon stores that claimed to be the "official" ones. Here are the main websites of each:
I just want to add that your warning about buying a hardware wallet from Ebay or Amazon is valid, however these companies have official resellers.
Ledger's Reseller Network consists of a group of official stores available worldwide. One can even
apply to become an official Ledger reseller. A part of the reseller team is their Amazon Network with stores in the US, UK, France, Spain, Canada, Germany, Italy, and Japan. It's OK to buy from these stores as long as you reach out to them from Ledger's official website and not by searching for 'Ledger Nano S' on Ebay/Amazon, for example.
Trezor also links to a bunch of
official resellers from their website. But none of them are on Amazon or Ebay.