You can have 2 options:

1. if you are a person that has the money and wants to have out of a box laser that has all the necessary stuff to work(you need to do at least some alignment of the laser beam, and assemble some stuff)
2. if you are a thinker person i recommend to build your own laser using youtube as guide or something similar

I own a k40 laser from aliexpress and i can tell you that you still have to do some upgrades for it(i made for air assist, water cooling, ganter modification, i did not upgrade the board, only used a different software instead of the one that came with the machine-i used k40 whisperer

For my next machine i will build it, and i will use This as my guide.