FWIW here’s a long thread about things laser:
I’m quite happy with my JTech add-on since I did not have room for a standalone laser engraver, other folks think it is way too expensive and source various chinese parts themselves, and @RichCournoyer seems to be very happy with the Ortur laser machine he bought (but that’s not a conversion, it’s “just” a cheaper way to get a lasering capability if you don’t need the integration with the Shapeoko). Whatever you choose, please be safe / add a variety of safety physical interlocks in your setup, I know it’s obvious but rather said too many times than not enough.