Luxeon K2 TFFC Part nos:
LXK2-PWC4-0180
LXK2-PWC4-0200
LXK2-PWC4-0220
LXK2-PWC4-0240
Right now the seoul is the best choice but the K2 TFFC is almost a direct drop in for most lights, just not available at the moment.
They are slightly larger, but the dome and the die themselves are the same size.