http://www.ipscstore.eu/en/tanfoglio/974-tanfoglio-sear-spring-2000000009742.htmlThis will add a few grams due to higher coils than standard CZ sear spring, not sure how much. I feel it might not be enough for 300 grams of increased weight.
I did something different.
I added approx 1 full pound of trigger weight by using two standard sear springs in place of one.
Before/After/IncreaseLowest point of trigger: 1 lb 4 oz / 2 lb 4 oz / 1 lb increase
Middle of trigger: 1 lb 12 oz /3 lb 6 oz / 1 lb 10 oz increase
This got the trigger to end up perfectly fine for 1000gr weight requirement.
I had to open up the space in the sear to accommodate for the 2nd sear spring. I used services of an edm cutter at a workshop, but can be done with a dremel too at home.
I would suggest you order a spare sear, and a couple of sear springs to work on. I have done this on two TS with similar results.
http://www.ipscstore.eu/en/cz-tactical-sport/504-cz-75-ts-sear-2000000005041.htmlI do not think you could use a standard CZ75 trigger return spring, due to different trigger bar in TS vs other CZ75 pistols. If you could somehow, then using that as well as the tanfoglio sear spring might get you above 1000gr, but I cannot say for sure. Double sear spring modification needs some work, but works like a charm.