I installed stronger 0.8 mm searspring (link below) in my TS2 and it increased my trigger to around 2.4 pounds. You can see the sear spring is much thicker and stronger.
https://www.cz-parts.com/cz-shadow-2-cz-ts-2-cz-75b-sp-01-sear-springTo get it to 3 pounds I think only option is opening up the sear to be able to install two sear spring, e.g standard plus 0.75 mm. I tried with 0.8 mm + standard sear spring and it got my trigger to approx. 3.7 pounds.
To make space in the sear for second spring, it’s either gunsmith or Dremel tool.
The picture above is with two standard TS sear springs and it got my trigger to 2.2 pounds. Later I received 0.8 mm sear spring mentioned earlier and combining it with standard TS spring it got me to 3.7 pounds which was way too much for me. It’s when I realized 0.8 mm version adds quite some weight so I tried it solo and it got me to 2.4 pounds which is perfect for me.
I strongly recommend you also buy new sear and keep the original for backup.
P.S. I also tried Tangfolio spring which did close to nothing for me, adding less then 2 oz.