The dealers used to carry them, but I suppose that none do for such old cars anymore. Motorsport Auto used to have them too.
I've used an air vacuum to retrieve the little buggers from cavities. Air vacs use a 3/4" vinyl hose, and I stick one size smaller inside of that to get some reach into those deep places around the wheel arches.
And look for the weep holes where the quarter panel skin is spot welded to the inner unibody structure.Sometimes you can blow shop air into them and find all kinds of stuff.
Instead of flares, why not fat fenders? Like these: