I have not ever noticed any and had a quick google just now with no results. You might be better off uprating suspension bushes and checking existing suspension for wear (ie ball joints and track rod ends. Bushes to look for are: Anti roll bar clamps, inner tca and the doughnut bushes on each side of the ARB. If you can find a cheap damper/spring set as well on top of that your car should feel quite tight.

It's just an idea but you might be able to fabricate your own lower brace if you have the tools?