Where can I get a new Logic Board

My iphone got dunked in the Ocean and when I went to clean it I noticed scorring on the connectors. After cleaning it and connecting the display and battery and connecting it to my chager I got a black screen with the intermitent bong noise.

After researching I determined that it was telling me there was something wrong with the display, so I ordered a new display and that didnt fix it (incidently when I connect it to my computer the computer recognizes it but I couldn't save any data because it was locked and I had to unlock from the phone (argh!).

I then ordered a new display and after connecting it, I got the same issue and am now concluding its the logic board.

So we now get to my question, where can I buy a new logic board that is clean and I can restore my phone to it?