Not local, but www.onlinemetals.com is where I get most of my plate from. Cheaper than most and no charge for cutting to the size you want. T6 refers to temper - not aluminum grade, so there's really no such thing as "T6 aluminum". Get Type 6061 in a T6 temper - machines decently, cheap, strong and doesn't corrode as much as some others. If you need superior strength, try type 7075. 24" X 24" in 6061 will run ya $130, type 7075 is $200 Both are readily available although the 7075 will cost a tad more.