Great, good to know you guys can use the Sparrow bars with no folding (or handling) issues.
I guess there will always be some tradeoff with the folded size if uses anything other than a flat bar. The loop type bars are interesting but they do seem bulky.
I found this video of a Tern bike with bullhorn bars (which shows it folded, and it's not bad but the bullhorns do stick out significantly.) But maybe something like a very short bullhorn would work, with just enough curve for an additional hand position.