I have some brake pads made in Germany, I think (Landesgewerbeanstalt Bayern) that are guaranteed not to squeal. I use them on my cross bike. It looks like they will fit Mafacs although they will not look original. I measured the post size and they are almost identical.
I'd try them on my bent seat tube Bob Jackson tandem but it is currently in use as a hanger for tires and buried in the back of my garage. If someone is interested in trying them, they're $10 including shipping. If they don't work you can send them back, I'll be able to use them.
I'll be at the San Diego swap meet Sunday and should have a big selection of tubulars from $15 up to $50. Look for the Tufo sign.
Jim Cushing-murray
Del Mar CA