I just looked in my Studiospares catalogue and they's got 4 pole speakon cable connectors at £3.30 and the coupler (which you'll need if you ever need the full 100m again) for £3.99. Translated into dollars and adding shipping to the USA (Studiospares are German + English) I don't know if that works out cheaper.
Have you tried a Google search? There must be a US supplier who'd be cheaper on the postage. But Studiospares will happily ship anywhere, at cost, by your choice of courier, it says here....