They make them Mark's Bagel Place in Dresher - not bad, but not quite right either. Worth a try if you live nearby. I second bringing them in from NY and freezing - every time I go back I bring like 4dz bagels/bialys.
I've never had a good bialy in Philadelphia (and I've looked)....you'll have to make an excuse to visit NYC and bring some home. Sometimes Famous 4th Street has them, but there doesn't seem to by any rhyme or reason as to when or how many.
On Sundays, ShopRite in Cherry Hill has a table with 20-30 large paper bags of bagels and bialys. I don't know where they are from (trucked in from NY? Don't know) but they are pretty good. The bialys tend to be a bit thicker than the NY ones but the minced onion is there & good.