Sucks, but do you have a picture to assess the damage? Don't you have repair kit that came with the board? If not You can order the proper material online (or local shop including rafting companies) and DIY. It is not too difficult but follow the steps meticulously..

Paroskite Resort, Paros has rental gear.. Their location has a strong venturi effect even if the Melten is quit often strong enough
Just a step away (next island) Mikri Vigla Beach, Naxos has rental gear..