If you mean more power, then you are kind of stuck. Each laser you buy is most likely operating at the highest power it is capable of. Even if you could increase it's power, which is almost always more difficult than connecting it to a "stronger" power source (whatever that means), you would greatly reduce it's lifetime.
If you mean you want a beam with a greater diameter, then that is much easier. What you need is some form of a telescope to expand the beam. This could be as simple as 2 lenses (a Galilean telescope). Search google for "laser beam expander" to get more ideas. if you have a fixed target distance, and you just want a larger spot, then a single lens will do.
Khanacademy has some good introductory videos about lenses, like this one:
https://www.khanacademy.org/science/physics/geometric-optics/lenses/v/multiple-lens-systems