You can pick them up from Yahoo Japan for under 5k yen for a used one + shipping and fees though the last one I bought made by Dolphin only cost me 1k + fees, bargain
I understand that you may be wanting a different asthetic for your engine bay, but if it weight you are trying to save, the stock one is fairly light anyway... the 2 kg saving (guess) isn't really worth it unless the interior is stripped etc...
The best way to reduce weight is go on a diet... well for us overweight fellas. (not having a go at anyone)
I don't recon you'd shave as much as 2kg between braces unless you had one made of CF - the stock one can't weigh much more than that in the first place!
Yeah the stock one is pretty light! And chunky as hell too - most aftermarket ones would surely struggle to match it for rigidity, which, after all, is what it is for...
I have to agree that the stock brace is very good IMO. It certainly makes a difference.
For #$%^ and giggles I took my front strut brace off (when I was mucking around fitting the rear brace), and went for a drive; it makes a very big improvement over the handling without it. From what I can see Mitsubishi did the R&D on the stock item and it serves its purpose very well considering. Unlike those cheap "after market" ebay specials you see hardly making a change to the body during cornering.
As it has been said; I don't really see the point to change it unless you are building a race car, where every gram counts; or building autosalon's next winning show car... even then I would probably just paint it at the most.
I actually quite like the way it has cut-outs and the rise over the top of the throttle body, looks a damn side more attractive then a plain flat bar in your engine bay.