I fixed my noisy soccer ball motor for 5$ and it is a job you can do in 5 minutes.
I had purchased a replacement motor from Marco supplies, and to be honest it was even louder than the old one... MUCH louder. It sounded like a remote control electric car was 5 inches from my ear every time it turned on... I wonder what their return policy is.
In any case, before I reinstalled the old one, I took it apart and saw that there was 25 years of gunk in there. After some research, I cleaned the motor with a paper towel and squirted in some Lithium Grease (5$ at Home Depot in the Automotive Section) and hooked it back up. It is MUCH quieter. You can still hear it, but it is not nearly as loud, spins up faster, and continues to spin a little even after the motor stops sometimes.
If you wanted to do this yourself, you can do it without having to solder anything and by only removing 2 screws. If you look at the motor, it separates from the gearbox with 2 flathead screws. If you remove those, the motor will pop out leaving the gearbox. As you can see from my photo it was filthy. I gently wiped it with a paper towel and squirted in the lithium grease. Make sure you do not lose the little black O ring. The whole process should take maybe 5 minutes.20180901_061459 (resized).jpg20180901_061647 (resized).jpg20180901_165027 (1) (resized).jpg