I have been looking for a Lankan restaurant, good or terrible, in the Philly area since I came back to this place from Australia & Toronto (CAN) some 10 years ago.
Unfortunately, the closest you'll get to any Sri Lankan eating spots is in NY, a couple which are ridiculously priced (located, as of this date, on the Upper East Side).
Even the few Lankan spots in North NJ have closed.
To me, other than going to Colombo or some other SL city, the best place to find a good selection of SL restaurants is in the Sydney western suburbs. There are a couple of good'uns in Auburn NSW. (Before ya suggest it, yes it is my intent to leave my beloved but 'goofy' native country here just as soon as my time is up in the USNavy - on back to Ozland.)
I'm always looking for SL foods in the MidAtlantic states. Should I see any I'll be sure to come back here and give ya the hedzup.
Good luck, mate.