We just looked at brace problem together with few grease monkeys friends :)
After analysis and building Autocad model of it we came to conclusion that very few aftermarket braces really do it well. But...if choice is down to aftermarket.
One brace that looks OK it Stefan Hessler brace.
Also one of guys in our "team" got his DR650 (last model line) with brace and it does look remarkably good, but we failed to find who and where made it. It certainly not self made.
Conclusion is: only aftermarket brace we could find specifically for DR is Hessler's item.
Only potential candidate from other bike - DR650 brace (same 43 forks) but we need to check distance between fork legs, it might be different. Working on it.
Also may be Africa Twin aftermarket brace would fit, but I do not have now access ot AT to measure distance between fork pipes.