25acp is THE mouse cartridge, but i'd enjoy a reliable larger 25acp gun as well. I believe the largest in my collection is the phoenix arms HP 25 or possibly the taurus PT-25
This seems like a contender for largest: https://en.wikipedia.org/wiki/JO.LO.AR.
and HK 4 seems worth mentioning, https://en.wikipedia.org/wiki/Heckler_%26_Koch_HK4
Not a big fan of derringers, but smaller ones of this style or the south american garrucha style derringers are neat to me. I've heard butler derringers often fail to fire. I'll find that out next time I go to the range - but obviously I got it just for collection purposes.
The closest competitor to an NAA mini is the mini revolver offered by standard manufacturing, however it has a very short barrel at 0.75" and it is more expensive.
I'd be potentially interested but the cost and sub inch barrel puts me off, the one thing it might do better is the opening mechanism for the folding grip. IMO the NAA mini folder is a bit too stiff and would be better if it was spring assisted.
If you've shot the "switch gun", let me know your thoughts on the grip and how good the build quality is overall. Thanks!