If it's an ISIS bottom bracket/crank interface, then there are other cranksets available; for instance, Nashbar lists a couple of ISIS house-brand cranksets. Is the Truvativ crank a splined interface with internal bearings? That would be ISIS. Finding just a right crank arm could be hard and possibly not cost-effective.
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Bacchetta Giro A20, RANS V-Rex, RANS Screamer