Tire shopping by size and bikes for little people...

I have noticed that it's really difficult to shop for bicycle tires by
ISO size--not only for all tires (or just all major brand names) but
even within a single tire company's website. Is there any way to do this
other than just using Google?
,,,
A particular example is that I went looking for the sizes that Kenda
Kwest tires could be had in, since I couldn't find any listed for a
couple odd sizes (355 and 507mm). Because there isn't. But even on the
Kenda website, the Kwest isn't listed under "road" or "commuting" tires,
it is listed as a racing tire in the wheelchair category,,, even tho the
smallest size made is 20" / 406mm (that's a little wheelchair to be out
racing, I'd think). And the Kwests are 1.5" wide, quite a lot wider than
the commonly-used tires for wheelchair racing that I've seen elsewhere.

The manufacturer sites prefer to list the tires by model and then size,
with no way to search for a particular size across all models they
currently make. Some even kinda bury models that aren't from the current
year.

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Also I got curious about 650c tires, and found that most all tri bikes
are back to using 700c sizes. Some companies still use 650c for their
smallest frame sizes. A couple companies are building custom frames for
the 520 or 540mm sizes (Terry ect). Are most short people just suffering
on 700c bikes now, or are they clinging to ancient 650c bikes?