For future reference, I would suggest you check out samuels and son seafood.. they are outta the philly area. Also, seafoods.com and honolulu fish company both do overnight flights which typically works best on finding a true hawaiian supply.
Only 1 word of caution, if you order the fish as AHI.. you may not actually get what your looking for. The term AHI is a hawaiian generic term for tuna, but in reality there is no "ahi" tuna. It has to be a species, then grade... Typically for purposes of a Poke dish you could get away with a 2+ loin of Big Eye. Big Eye tuna has a much better fat content to their Yellowfin counterparts, and as it will be cut up a 2+ will probably work best for you.
I spec 2 tunas on my menu. A 2+ yellowfin.. which I typically use as a steak cut and a #1 Bigeye which I use on mostly raw dishes. Personally I run my poke with BigEye's but the cost point on them makes them a bit harder. Nothing is better than a fatty tuna!
I know of folks who have used Tombo for years in such applications (Tombo is the hawaiian name for albacore) but the lean nature of the meat makes it unacceptable to me. However the price point on such a fish in likely less than half of what a typically big eye loin sells for.