bikepartsusa.com, nashbar.com, and a few other sites sell new forks, but they're a bit costly. You might be better off finding another peugeot (i.e. a UO-8 from a similar year) and swapping everything over.

As far as triples, I'd just go with one that's completely polished or satin, don't get one that's black.

Being for your mom, I'd go with upright bars and either stem shifters or thumb shifters. I'd also seriously think about just using a single chainring up front that is somewhere around 40 teeth, then get a good 7-8 speed hub for the back. that way you can run a chain guard, as well as fenders.