The Souljourner said:It's one of their drawbacks (along with making you look ridiculous, with these planetoids orbiting around you).
The Souljourner said:That's the way all magic items work - do enough damage and they're destroyed. Ioun stones are a special case only because they're not being worn, so they're a lot easier to hit (worn items in general can't be hit, and held items require a sunder attempt). It's one of their drawbacks (along with making you look ridiculous, with these planetoids orbiting around you).
Gort said:Using the magic item creation rules, simply make something else that's slotless with an identical effect. Same cost, and without the vulnerability.