Siosin -- I completely understand your frustration! I want one badly as well, but completely missed my chance, too. :'( These Yili horses sold out completely by approximately April 2019, and then were only available sporadically from re-sellers for a few months after. The places that said they would have them back in stock never got them in again. I believe they were a very limited run and also very popular, and sold out completely.
I actually contacted someone who is connected to Mr.Z company (I believe they are part of the side company that sculpts some of Mr.Z's canine sculptures), and even asked them if any more Yili horses would ever be made. They sounded like there was not much of a chance of that, unfortunately. I did explain how nice these horses were (the best mass-produced 1/6 horses I've seen so far) and that I thought if they could create something comparable, it would also sell very well. They told me further equine models would be produced, but probably new/different ones, and to look out for those in future.
Well, many months later and we had an announcment for the Mr. Z 'Golden Horse' Akhal-Teke model:
https://onesixthfigures.forumotion.com/t2977-new-product-mr-z-1-6th-simulation-animal-no-48-akhal-teke-golden-horse-blood-sweat-bmw-full-set-of-6-colors?highlight=akhal+tekeIt's not as good a pose as the Yili (at least for me, I prefer neutral, non-action poses it those are more versatile), but it is a nice looking model, which seems similar to the taller size/height of the Yili model.
These are still available for pre-order, but they seem to be going fast.
Alternatively, there are also still some of the Mr.Z 'Hanoverian' model available:
https://www.ebay.co.uk/itm/1-6th-Mr-Z-Animal-Germany-Hanoverian-Horse-Fit-12-Soldier-Figure-Race-Horses/173910317879?hash=item287ddcdb37:g:DrQAAOSwoDNc5MPx
These are decent 1/6 horses (better than a lot out there). The only downside is they are a bit shorter in stature, and for some people's tastes are thus a bit awkward for taller male action figures to ride. Personally I don't mind this model, I think it is quite cute, albeit completely misnamed as it looks nothing like an actual Hanoverian warmblood (looks more like some kind of Arabian/Quarter Horse mix). I'm planning to use my Mr.Z Hanoverian as a mount for a petite female character, so I think it will work out ok. : )
Which horses appeal to you depends on personal taste -- of all the ones released by Mr.Z so far, the Yili was the most attractive to my eyes, but sadly I missed out. So I have the Mr.Z Hanoverian and Mr. Z. Shire horse (the Shire is also now sold out) instead, and they are both very well-made models that I am happy to own. I'm definitely considering a Mr.Z Akhal-Teke, as I will probably regret it if I miss out on that one too.
Mr.Z also recently put out an 'Arabian' model, which I personally am not overly keen on, but others might be interested so I'll link to it here:
https://onesixthfigures.forumotion.com/t3152-new-product-mr-z-1-6-imitation-animal-no-51-arabian-horse-full-set-of-5-colors?highlight=mr+z+arabianThere are other mass-produced 1/6 scale horses made by different companies, but in my opinion most of them are nowhere near the same quality as Mr.Z horses.