Touchstones can generate in hardware stores.

Artifact unaligned touchstone called Grinder: rubbing it on or applying it to an object repairs one level of rust or corrosion but decreases enchantment by 1 (which can go negative). Invoking it cancels a single object.

YAFM for when polymorphed into a glass golem and you rub a touchstone against “-“.

Gnomes spawned with a sufficiently high starting level, or else just a fixed percentage of gnome lords and a different fixed percentage of gnome kings, generate with a touchstone.

Touchstones no longer count as magical items. (Real-life touchstones aren’t.)

Increase the damage of slung touchstones. Thrown luckstones retain their lowish damage but have a chance of getting “lucky” hits that do much more damage or instakill monsters.