I just did this repair on my van, for spacers I actually found a piece of aluminum hollow round stock that was 1mm thick and 10mm outside diameter. I cut pieces to size, and they fit nice and snug inside the bolt holes, leaving no room for play between the bushings or the bolts!
It'd be interesting to see how the aluminum lasts over time, vs steel.
"If you find yourself holding a sledgehammer or a crowbar, it's time for a break."