My first quad used KEDA KA22-15M motors. These motors are powerful for their size and they have a KV rating (unloaded RPM/Volt) of 1050, almost perfect for a 11 X 4.5" prop (11 inches in diameter with a 4.5" pitch) and a 3 cell (12.6V) battery.
These motors are used on two of my quads, and when I went to buy spares, I found that Hobby King no longer sold them. I had to buy them from Strong Motors in Michigan.
I may know why they are getting hard to find - they do have some problems. The most serious is that their shaft has a groove for a snap ring which keeps the motor together. The groove is not really wide enough for the snap ring (or 'E' clip), and will sometimes come off. I found this problem early on when I put my quad into a hard climb, and the propeller and the rotating armature flew off upwards. The quad then came crashing to the ground, of course.
I had a several of these motors and I didn't want to throw them away (or send them back) so I made a "jig" with three short pieces of a 1 X 4 and a hinge. One piece was clamped to the table of the drill press. Another extended upwards at right angles and was fastened to the first piece with drywall screws. One side of the hinge was connected to that "vertical" piece. The third 1 X 4 was connected to the other side of the hinge. This piece could swing toward the chuck of the drill press and was parallel to the drill press table. I used two large tie-wraps and fastened a Dremel tool with a light-duty cut-off wheel (abrasive disk) in its chuck. Then I put the 3mm motor shaft in the drill press and spun it. I then moved the Dremel over to the shaft and let the abrasive disk cut a deeper, wider groove in the hardened steel shaft. That provided a perfect solution to the inadequate shaft attachment problems. I cut some nice grooves in hardened steel shafts without having to take them to a machine shop.
Today, I went flying with one of the quads that had those motors. It was flying great! Then I pushed the throttle all the way up. A prop (and motor bell) went up to the sky and the quad came crashing down! I had forgotten to rework the shaft of that motor! Fortunately, I had a spare prop and I could re-print a broken piece with my 3D printer. I re-grooved the shaft, printed the new piece and put everything back together. Now, an hour later, it is ready to fly again.