I have a plethora of holsters for my Glock 19. My advice - first decide what you want to use the holster for, and then decide whether you plan to get other 9mm Glocks (G26, G17). If you may get others, then get a holster that will accommodate multiple lengths of gun, meaning an open end style.
If you want to wear it IWB with deep concealment, then I'd recommend either a Crossbreed Supertuck or Milt Sparks Versa Max 2.
If you want an OWB holster, and don't mind taking your belt on and off, there are a ton of great choices. It really just comes down to taste and budget. I have not tried the guy that Charles recommends, but I do have an Adams Leather Works holster for my G26 that I love, a Galco for my G19 that works great, and I also love Tucker Gunleather holsters.
If you want a holster that you can easily take on and off (without removing your belt), then go with a paddle style. Fobus is cheap but works OK. Or you could go high end and get something like a Kramer Gunleather MSP paddle holster.
Sorry I couldn't be of more help, but like most I have a whole drawer of holsters for various guns and carry purposes.