In Boston: Calumet Photo, by the
Galeria mall in Cambridge (just over the river from Boston -- literally closer to downtown Boston than most of Boston is) carries Pentax, although their selection is small and random. (For a while, the three lenses they had in stock were the DA★ 16-50, DA★ 50-135, and DA 14mm.)
They're sometimes a little rude there if your appearance and demeanor don't scream "Pro Photographer". They'll sometimes match B&H's prices, but not always.
Also, I'll second the suggestion to go with B&H Photo. They're in New York, and one of two NY camera stores (the other being Adorama) which I trust to not scam people. I order from them all the time, and I've never had my purchase show up later than the next day, even with the cheapest shipping.