Where do I find a power supply(wall wart) for this TT? Can this power supply be upgraded?
If it uses a wall wart then you can upgrade it; look under regulated power supplies.
I'm pretty sure the Pro-Ject Speed Box would work with it. Music Hall has a version with their name on it too. The Speed Box is a very big upgrade on the Pro-Ject decks, which have the same motor (and other stuff) as the Music Hall decks.

Call the Needle Doctor or Music Direct. They should be able to conform or refute.
I have a MMF7 and use the Project Speedbox with it. Sounds marvelous. Highly recommended!