I'll have to get a 5v motor with gears I think!
A better way to do this is to look at what you want the motor for and search for a motor that fits the bill. That may or may not be 5V. Even if it is 5V you can't drive it from the Arduino, so looking or hoping for a suitable 5V motor is neither here nor there. If the best motor for the job happens to be 12V or 9 or 24 or 5, whatever, just find a power supply at that voltage with sufficient current.
Then control that with the Arduino, through a suitable transistor or if you need direction control, a driver module like the good ones Pololu have. They have a huge range, various voltages and currents. (Best not to use old chips like 298s or 293s.)