You can buy an expensive tool, or pay a bike shop to do it, or you can DIY it in 30 seconds flat.
Stick a 6mm hex key into the upper pivot bolt, and bring it back into line by eye. The upper pivot bolt is strong enough to do the job, and will take the hanger with it the same way the tool does. Of course you won't get the precision that you could get with the tools gauge feature, but for an older 8s bike it's good enough for government work.
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