Please read this entire site which should quickly disabuse you of the notion that the technology is simple.
The reality is that high speed laser communication (ie, slow by today's standards 10mbps) is not at all trivial, and particularly over the distances you need. There are so many tradeoffs involved in the optical path alone that you could spend months or years trying to design something that would connect at all, nevermind provide a reliable link. For instance, do you select a lower divergence, which gets more power to the end point, but means that if either end moves more than a micrometer then the connection is lost, or do you have a larger divergence which makes aiming less critical, but delivers such low power you have a hard time receiving?
That's just one of many, many trade offs and losses in the optical path engineering, and doesn't even touch the necessary low noise amplifiers and electronics, nor the physical layer interface to the network(s) or computer(s) involved in the communications. This also ignores the regulations of laser emissions in a city.
At any rate, if your requirements are
- Laser communications
- Up to 5km distance
- Home budget size
Then the answer to your question, "Do they exist?" is no.