One of the few ultralight bipes that I recall was the Hyperlight - a scaled down version of the Hyperbipe. I knew only one individual that had one of these but he loved it. However I'm not sure if the kit or the plans are available any longer.
Another lightweight biplane you could look at is the Micro-Mong :ban:
It's a bit smaller than the Acro-Lite and completely available as a kit.
'Mong' does state that the Micro-Mong is not aerobatic, but.....
I once saw a little biplane (this was in Europe) whose wings were made from AN2 ailerons! Yes the big Antonov AN2, radial engined, monster-biplane. It looked quite well made and it may even have been built at a former Soviet aircraft facility, but my memory is hazy now.