Spyderco Techno. They are releasing a Techno 2 either shortly or already have. For another great tough Spyderco that is even smaller check out the new Spyderco McBee.
Something really tiny; Rike Hummingbird
Spyderco Flathead is also quite small, you can wear it around your neck like a dog tag too so it will always be easily accessible.
Also I don’t know if Autos are legal where you live but there are quite small Protech knives. Then there is the 2.4 inch otf auto UTX-70 from Microtech.
Another one is the Bestech Goblin.
There are alot of good options out there. Some knife websites let you filter by blade length
Blade HQ: has no 2.5 inch and under filter, but has a 2 inch or less filter. You might try some other sites which may have filters more exact to your desires.
Blade HQ folders under 2 inch:
https://www.bladehq.com/cat--Manual-Knives--45#/filter:blade_length:*:2