引用自 Crispy：

Are there any traders that sell laser upgrade kits? If not, what's the best way to get them?

This site is very useful for finding where to obtain all the different items in RE2: https://empyrionbuddy.com/item/LaserKit/re2/english

Spoilers obviously.

Other than buying the kit, you can also get them from deconstructing laser rifles.

Laser zirax also drop them

Best way to accumulate them in the necessary numbers is by using your Base Teleporter to visit Half a dozen or more Polaris trade stations in a cycle. Teleport back to your base after each jump to make sure you are not teleporting out of your home-base range.