Are you referring to the road bikes that Peugeot built back in the '70s with Reynolds 531 double butted frame tubing? If so, those were originally equipped with tubular (sew-up) tires, which I seriously doubt you'll ever see at Wal-Mart. Presumably the rims have been replaced with clincher rims, so the question is, what size rims? If it has 700C rims (bead seat diameter = 622 mm), then there are loads of high quality tires available to choose from. 700C rims would be an exact swap for the original tubular rims, but people did put 27" rims on those bikes. If that's the case then you're options are limited to the lower end of the price scale, maybe not Wal-Mart but not top of the line tires.
What did your friend/mechanic say was wrong with the tires?