Metal spurs are normally only used in high torque and offroad situations... so I don't know if anything would exist for your on-road needs.
Check Robinson, GH and maybe Hardcore. I know all of those make spurs for different vehicles, but I don't recall any of them being on-road.
Aluminum will also transfer heat, so keep that in mind if your using it on a twospeed setup if you find it. The extra heat from the engine may mess up the clutch shoes themselves.
I don't know on-road, but from what I've seen, the two speed trans are external an run right off the engine instead of being inside of a trans case like the maxx or savage.