Isn't that related to the skill trick "Tumble in the Sheets?"
OK, I get it - reduce your armor check penalty. Valid, but I am hoping for actually increasing the skill, not reducing potential penalties...
Magic Items? I mean, it would be easy enough to create one that give a competence bonus to Tumble.
As far as magic items, I know in theory you cna make one, but it would be a much easier sell to a DM if I could point at an existing item that boosts Tumble...
Another idea - any way to take 10 or 20 on Tumble while under stress?
I believe you'd need a class feature that allows that. While I'm fairly sure I've seen some prestige classes with that ability, I don't know what they are off the top of my head.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.