Nope....not a whole lotta rust on mine, comparitive to other none restored 33 year old Mustangs......bottom 2 corners of each door (very common on old stangs, replaced), lower quarter panels (already replaced), section of trunk floor (replaced already, too), engine compartment panel behind the battery tray, front radiator support panel, and front engine compartment panel on driver's side (all 3 replaced), front section of passenger's floor panel (soon to be replaced)....that sounds like a lot...But really, for this year and model, not too bad....
No, I'm not sure where you can the part you're looking for. Tried Mustangs Unlimited or California Mustang? National Parts Depot is another good one.