Couldn't contain myself, and just built one up using the 5/32" bearings from a headset race.
There were 22 bearings in the race, same as the number in a pedal which is fortunate.
I could have got another bearing in each side, so maybe they are a tad small but I think they'll do fine.
When I got the pedals they were rusted solid, good to see them spinning now.
What bikes did Maxy pedals come on? MK1 Burners?
Edit >>
I just realised, the bearings are probably the right size, it's the cups that will be worn down.