New sealed bearings in vintage hubs?

I will build my first wheelset this summer.

I have looked at vintage hubs with sealed bearings (e.g. Pelissier Alpin, Mavic 500 / 550 RD and more).

And my question: Is it possible to find new bearings to replace the old if / when they are worn out?

I would appreciate your experience on this issue. If anything generel can be said. Thanks.

(And I did search the forum before posting this!)

According to this picture the Mavic's at least will disassemble to reveal a regular bearing cartridge inside. Not familiar with the others. Also, you may or may not special tools to get them open.

http://www.equusbicycle.com/bike/mavic/images/17and18.jpg

theoretically you should be able to replace them with new units, but whether or not they are a standard off the shelf size and easy to get hold of is another question. You'd need to pop the bearings out and check for any codes on them

I'm guessing here, but with the French hubs at least you are talking about sealed units that are metric, so theoretically you should be able to source bearing units to fit.

This is a genuine Mavic 500 rebuild kit - as you can see, the bearings are exactly the same as the ones you'd find today.

Sorry for the monster pic!