I'd go with the Hatsan Blitz, it is available in .177.
Just had a look but have they discontinued the .177 version for the first Blitz?
The new Blitz BP (bull pup) is available in .177 listed on hatsans website but not sure if it's available in the US yet if that's where you are.
It is much longer than what you want though. The Blitz can be really finnicky, you might need to make a lot of adjustments to the rifle to get it to function correctly (like increase spring tension in magazine and increase hammer spring to increase air to make the cycling work better).
Not really sure what your intended use is, you could go with a Umarex Steelstorm and buy the Co² to HPA adapter.
Just target practice or do you need it for pest control? Pellet or BB?
I'm most familiar with Hatsan and they don't really have any short semi auto rifles other than the Bullmaster, the Sortie is a pistol.
Kral seems to have quite a few options that are short and semi auto.
Kral Puncher Ekinoks is semi auto but too long.
There is a Kral Puncher NP-04 that is semi auto but only in .22 and .25 from what I could find. It's not even listed on krals official website yet but available for sale in europe. It would be perfect for you if only it was available in .177 as it's the same gun you already own by semi-auto.
It might be discontinued or heavily delayed as I
found a video that is 5 years old showing it at some convention?
I couldn't find a single video in english about it so perhaps it's only available in certain regions?
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If BB is ok then you probably have over 100 options in pistols, smgs etc but you will have to convert the Co² to HPA if PCP is important to you.