You won't be able to get direct help from Apple or through an Apple Store as you are NOT an Aurhorized Apple Technician.
If you have another Authorized Apple reseller/repair center that you can locate in and around your region, you maybe able to have that authorized Apple center order the part for you.
If Is this a connector that was soldered to the Logic Board, if you find an authorized Apple repair center that can resolder the old connector OR desolder/resolder a new purchased replacement connector that would be best.
Otherwise, you are out of luck and will have to pay to get a new,replacement Logic board.
This is what happens when someone, like yourself, who maybe a newbie/novice with Macs and with iMacs that decides to break into a Mac that was never designed for the inexperienced users to tinker with and upgrade these style Macs.
This is a very difficult Mac model to work on for very experienced Mac upgraders!
I consider myself very experienced with upgrading Macs over the years, and even I won't break into these new, aluminum style iMacs.
Apple designers and engineers have made these iMacs pretty much a daunting and tedious task for an end user to upgrade anything or work on anything inside of these Macs.
As you have found out the hard way, there a lot of fiddly, finicky small parts and connectors that can be prone to breakage.
I have given you my best advice, but bottom line you are now completely on your own to fix this, now.
If you need a new Logic board replacement, Apple MAY ( or may not) decide to help you and order and install a new logic board. This will be expensive.
You will have better luck with an authorized Apple reseller/repair center for the Logic Board replacement if it comes to that, but you'll still pay for the expensive replacement.
