Ask HN: Where can I buy a small software company?

So I currently have a software company that spins off a lot of cash and doesn't require much time to keep it running. I'd like to buy another software company / software product that I can work on and grow and make more money.

The problem, though, is wading through the crap that's out there on sites like flippa. Are there sites that have good, solid businesses for sale in the $50k - $500k range? A successful side project that the owner doesn't have time for any more?