Sounds like you also need cones as they stop the bearings falling out and the metal cover just stopped muck getting in.
Maillard hubs are largely bottom/middle quality and don't fetch a lot of money on
eBay so look out for a similar pair and transplant what you need (they did some good hubs - the prices will give you a clue).
From my experience the races in the hubs did not last well - you should start by looking at them for pitting (bad) and brinelling (not too bad) because if the races are gone then it's a waste of time looking for the rest.
You should also check the threading for the rear block - it will probably be French so you will need a French 5/6 etc speed block.