I have 6 plus spare 30 amp OPT - ESCs that I used on my DJI 550 and the worked great (no difference whatsoever)
Mine are in green heat shrink versus the original white is marketed by DJI. (and I know where to get the white heat shrink if you must have that color)
Mine are the Turnigy Multistar OPT 30 A ESCs that I have continued to use from some time now all the way up to my new Cinestar 8.
I will sell all 6 plus a spare to you for $30..... plus $10 to ship from Calgary Alberta where I live (no border shipping issues etc.)