Rel S3 subwoofer connection options?

Hello,

I just bought a very nice, slightly used Rel S3 subwoofer. Unfortuetletly, the seller did not include the Neutrik Speakon cable...As I see it, I have 3 options...track down a standard cable that should have been included...(least expensive option) Second, buy the wireless transmitter box $300) or buy the Rel Baseline Blue cable at $350? Any suggestions?

Andrew