I took some thick aluminum foil, made a small cone shaped patch that fit on the inside of the diaphragm, and used contact cement to attach it. Then it was just a matter of putting new white tubing inside, attaching the diaphragm to the needle bar, and cleaning/re-greasing the ball bearings.
Here's a video of it playing... It came out really good!
Also, thank you Wyatt for the help

https://www.youtube.com/watch?v=hsf6RC9loVk
Cheers,
David