I would like to announce that I have been able to stock the SATA female power connectors (15pin) at HW World. They have solder contacts to attach on a cable – this thing is almost impossible to get! You can clearly see it was originally not even meant this way as the body is still SMD (PCB-mount) type, just the contacts are different. So it is quite fragile and cracks easily, but at the moment it is the best you can get.
As modern computer power supply units often have only three molex connectors these days and this number will decrease, the worst nightmares are going to come true and the SATA will become the only possibility to get a few watts for your own toys inside your PC. The only advantage is that you also have +3.3 V on that thing so you can easily make adapters to different fan speeds without any resistor or other part. Refer to forums or HW World (czech only).