Still looking....for a month???? Any properly made maintenance driver will work. The SS one's are nicer. If you want a SANDING arbor, then NONE of the commonly made maintenance drivers will work. You need carbide. The SS will last for a while if you choose to use their OD(or turn them down), but sandpaper will wear them down and you will start getting inconsistencies.
If you want the cheapest possible get the aluminum. If you want cheap(less than 300 a set) carbide sanding mandrels I expect to see you "looking" for the next 5-10 years. A couple of people have tried to make them here and failed. Tom Migliore is your man...again.