I got my Lapras from a 10KM egg hatching. From speaking with other players, this is how they also got their Lapras.
I would also suggest investing in Incubators. They only cost about 39 cents each. Or, you can have some fun with Gyms in your neighborhood and earn free coins. You receive 10 coins for every Gym that you are able to place your own Pokeman into. Afterwards, open up Shop and click on the icon in the upper right hand corner. You will instantly receive your coins!
And with this program, we are constantly hatching eggs, which are quickly replaced at PokeStops. We have a limit for carrying 9 eggs, so it's always good to be working on hatching them, because we want those random 10KM eggs that show up.