My ideal would be one from Tom Bihn (www.tombihn.com
I'd never heard of them a few months ago. Was searching for a high quality laptop backpack, ordered 7 different models, demoed the heck out of them. Their Brain Bag was by far the best of the bunch. Ended up buying another piece from them, just super high quality stuff, incredibly well designed.
But I'd suspect the tennis bag market is a small niche, so we're stuck with what we've got.
That said, I'm still loving my Pacific Basalt bag. No complaints whatsoever, very functional.