There won't be a single source that has the breadth of Amazon's selection. But I'll often use Amazon to find the specific thing I want and grab the model number

There won't be a single source that has the breadth of Amazon's selection. But I'll often use Amazon to find the specific thing I want and grab the model number. Then I can search the manufacturer's website to see if they'll sell it to me directly. If not, Google it (or ebay or Cragslist or Mercari or...) which is much easier once you know exactly what you're looking for.