GOOD angle aluminum?

[BrianG]

Where can I get ~5mm thick angle 6061-T6 aluminum stock for making a motor mount?

I got this from Onlinemetals.com, but it's not a perfect 90 degree angle. I measure it at 89.549 degrees. That doesn't sound really bad but you can actually see that it is off, which wears the spur unevenly (and it IS obvious). I used 0.05mm thick washers as a spacer on one end to compensate in my BL Revo, but I'd rather get stuff that's what it is supposed to be.