You can check out this link for the sizes:
https://boomboxery.com/forum/threads/sanyo-m9994-belts.26590/
You can get them from various places including turntableneedles.com.
As far as the cleaner, most use Deoxit brand but there are others if you search.
This isn't the easiest deck to work on but it's doable if you're patient and take lots of pictures as you disassemble it.
I'd completely clean and lubricate the deck.
I've refurbished two of these and removed the deck completely from the chassis to make it easier to work on (again, take pics).
For $20, it's worth the money ($30+/- for the belts), time and effort to get it working again.