Isn't it always the way - when you no longer need it, something that was hard to get becomes commonly available?

Allbrite was fantastic for cleaning the old cast alloy VB/VC SL/E rims (15" versions of the HZ SL/E 14" rim). It used to be real hard to get back in the 90s - I sourced it from a commercial cleaning supplies place.
I agree with Adam - it worked well on wheels (didn't pit the machined rim surface), so it should do well on tags.