I usually get my angle stuff from onlinemetals.com. I had some extra 3.5mm thick angle stock left over from various projects, but can't seem to find what I did with it. If I happen to locate it, I'll let you know.
Phil - if you strike out on any of those, I can get you a piece of 6061 - just send me some shipping money. Not sure if I have any .125" thick though. What leg length are you needing?
Losi 8T 1.0, Savage Flux - XL style, LST XXL, Muggy, 3.3 E-Revo Conversion and sitting outside 425hp, 831 Tq Dodge Ram Turbo Diesel. It SMOKES