Unfortunately sub-5" phones are nearing extinction. The last holdout on the Android side was the Sony Xperia Compact line, and even that seems to have been discontinued.

All that's left now is a dwindling supply of existing models on the secondary market and a handful of extremely low-end Android phones.

Edit: There also the Sharp Aquos R2 compact, but it is only available in Japan.

It's definitely an under-saturated market. Some people fancy regular sized Pixels (of any gen). A family member of mine prefers small phone sizes, uses a Pixel on a regular basis, and it works for them. I expect the same for the newer gen non-XL models.

There are the really niche (and borderline fringy) ones you can find on Amazon. There are also some more general purpose Chinese phones for that. I'm not going to get into any of them because they're probably not what you're looking for, but they exist. (read: Unihertz phones)

On that note, there are the Nokia phones which are reasonably-enough sized, but nothing special. They're also quite terrible and overpriced as phones. The new Palm phone is also kinda fringy but worth considering.

A lot of these aren't really in this form factor, but phones are getting way too big and it's getting harder and harder to find really small phones like these (that can be reasonably used, ofc).