I managed to find a new piston from a tricycle driver in Tarlac I found on FB:
The piston number 13101-028-070 (std) corresponds to that on the manual I found online so I hope it’s right:
Here’s the new block I bought from Exact Motors back in Oct, 2019.
And here’s the headlight and speedometer assembly I bought from RetroMoto Vintage Japanese Motorcycle Parts
The problem is clear, it’s in blue while the bike is in red. I thought it would be in metal which would have made painting it easier since Republic Powdercoat is just nearby, but it’s plastic. I’m going to have to deal with that soon.