You can get it from any local hardware shop. Just take your cable along with you so that they get an idea which converter is needed for it. Congrats for the Box.
Well nish I bought some of those cheap 100 buck converters for my office but each of them went kaput after like few hrs of running. So later I had to get proper voltage transformer kit which is running suppa good till now and the reason for me suggesting for a better transformer.