U do not have to wear any armor at all... why should a mage do that? Would mess up predecided nature of "Plateless"...
But if you got to have armor... use Bracers
They can give +10 without being Epic...
Normal armor rules aply, (bonus squared) x 1000
10 x 10 x 1000 - 100000 aren't that expensive.. and +10 to armor for a mage, *yay*
Btw, when u reach higher levels... monsters have +60 to hit, as one of my players said,.. Why even wear armor.. they lower attacks are just 5 lower than the max.. They will jsut hit anyway..
Spend your money on something more useable