A well-known UK-based magazine for people who fly already has a database of aircraft for hire on its website. Unfortunately, it's very badly set up and hardly maintained at all, but it is a starting point if you're willing to search for 'Jetranger', 'Jet Ranger', 'B206', 'Bell 206', etc every time you want to find a particular type. (I would have gone with the G-INFO type designations for commonality).
On the more recent topic here, aircraft charter, like yacht charter, is an asymmetric business. Because there are people looking simply to offset some of their costs, not to run profitably, the 'buy some aircraft, lease them out, and return a profit' model hardly ever works, and certainly not in parts of the world where there is a competing, partial-cost-recovering, market.