Thanks everyone keeping the thread alive. I have compiled a short list of DAPs that could replace my Cowon Plenue D2 which has a screen so broken it stops responding to touch. Initially I thought I would have to go for a more expensive model (after all, Cowons were cheap for what they were) but after reading hundreds of pages, dozens of reviews and tens of youtube videos, I have concluded that all truly portable DAPs are in budget or low-mid segment which is helpful (to my wallet). Smaller DAPs also seem to never be flagships which means they are harder to find and if they are sold out, they are gone forever. Anyway, if anyone is looking for a
small DAP with good battery life that is still hifi, here you go. Remember, I am focused on compact size, battery life and sound quality (latter usually comes with a flexible enough EQ). Balanced output and physical buttons are strongly preferred . Everything else doesn't matter much (UI, streaming etc.)
SHMCI C4

Price: 50-70 USD
Easy to find: yes, new available on Aliexpress; I understand it is available under different names in European and US amazon shops too
Pros: 60 hours playback (better than Plenue D2 and almost as good as Plenue D...), reasonably compact
Cons: mixed reviews with regards to sound quality, no balanced output, seems like doesn't support SD card larger than 128GB. Objectively the ugliest one on the list.
Hidizs AP80PRO

Price: ~100-150 USD
Easy to find: yes, new available on Aliexpress
Cons: truly compact, amazing look and build, balanced output, reportedly great sound quality
Pros: battery better than modern flagships but still disappointing (<10 hours with balanced output, ~13 hours with single-ended)
Onkyo DP-S1
Price: ~200 USD if you can find it
Easy to find: no, but I saw some options on ebay that recently closed so if you monitor, I am sure you can pick it up
Pros: small, balanced output, reportedly great sound quality and build, battery life of 15 hours is decent
Cons: old model, like 7+ years old? I can't explain why it is a disadvantage, but I feel like Asian hi fi improves quite quickly and I suspect newer models are much better. Granted, I may be wrong. Otherwise, seems like a no-brainer choice.
Cowon Plenue D2

Price: used to be 300-400 USD
Easy to find: I couldn't
Pros: my favorite DAP ever. Small, great crystal clear neutral sound, JetEffect is the best EQ engine I have ever come across, 40+ hours battery, balanced output
Cons: I have been with Cowons for nearly two decades. Now that company is bankrupt, I may as well try something new instead of chasing old Cowon models. Also, SD card size is limited to 128GB which is not a major problem but still slight annoyance.
Sony NW-A306

Price: ~400 USD
Easy to find: yes, everywhere
Pros: reportedly great sound quality and features, battery is 20 hours or more
Cons: quite a bit more expensive than majority of this list, DAC used unknown (if exists at all?), no balanced output, still on a larger side.
HiBy R3 Pro Saber 2022 Winner so far

Price: used to be ~200 USD
Easy to find: no but with some luck can find second-hand
Pros: small, reportedly great sound quality and build, advanced EQ including proprietary engine, really small, balanced output, battery seems decent (15 hours balanced, 20 hours unbalanced)
Cons: ???
P.S. Shanlings have interesting options but it seems like they have many models that tick some of my boxes and no model that ticks all. M3X is too big to be truly portable, M2X is smaller but has poor battery, and entry-level models (e.g. M0) are too basic even for my frugal taste in portable audio. I didn't shortlist some other brands that are popular here (xDuoo, Aune, Zishan, Surfans etc. also Cayin, iBasso, FiiO) because they are either too big or battery life is too short, and both are very strong requirements for me.
Unless I come up with any new thoughts, I will go for Hiby R3 Pro Saber 2022.