well, there are a number of options availible to you.
firstly, there's materials - mithril makes the armor lighter and easier to wear, which provides a 10% reduction. but there's also living metal (from faerun), which only provides a 5% reduction but repairs itself over time (perfect for a ftr-mage warforged, if you can get your dm to swing with it). there's also blended quartz, out of Arms and Equipment. it actually makes the armor harder to wear overall (more wieght, higher check penalty) but it provides a 20% reduction.
secondly, there's enchantments - twilight. it's from the book of exalted deeds and provides a 10% reduction (it's only a +1 bonus, too).
finally, there's class abilities - rage mage provides a 10% reduction at second level, which works for most things. if you want to walk around in full plate and a tower shield, though, you cant go wrong with spell sword. it starts with a 10% reduction at first, and caps out at 35% at 9th. both these classes are from the complete warrior.
as an aside, the havoc mage (from mini handbook) gets an ability called battlecast, which allows the character to preform a single attack and cast a single spell as a full round action. the class doesnt provide any spell failure reduction, but it's still a nasty move if you can pull it off.
if you want to wear armor, make sure you're profeicent with it, as you'll suffer the armor check as a penalty to all your skill checks, including spot and listen (i think you also take a hit to your attacks, but i'm not sure) unless you are.