Fresh, whole crab
You can also try catching it yourself. Pretty easy to catch a good amount of blue crab with a few nets and some chicken.
All along the CT/RI shore docks and piers you can fish right off of. No permits needed, just need your catch to be of a certain size (usually 5 1/4" from tip to tip).
Most Oriental markets carry live Blue crabs or can get them for you and are usually very reasonable. Live Blue crabs are very common in Asian cookery.
There are company's in Maryland that sell and ship live but this method gets very expensive.
Where are you located? for specific recommendations.