In general, liquid propellants are so difficult to work with and so dangerous, and the rocket engines so difficult to design and build, that commercial engines only barely exist (and seem to be in the territory of rumor, possible Kickstarter scams, and dead Geocities links). Most efforts are more like amateur-operated-and-funded research programs than anything recognizable as mainstream amateur rocketry. Most tests seem to be static.
Liquid fueled engines are forbidden in the NAR and tolerated only by very special (and rarely granted) permission in the Tripoli rocket association. As sad as this is, it's the current state of the world. Perhaps in 20 years the cost of metal 3D printing will be lower and things might be different.
Hybrids seem to be slightly more common and more achievable, though they still have many problems.
The Reaction Research Society exists and provides some facilities and other assistance to people doing liquid fuel rocketry.