Okay, I did some "creative Googling" and found this:

"Chinese leaves are like a toss between a cabbage and a crunchy lettuce, with a delicious peppery flavour."

also --

"Chinese leaves
Also sometimes referred to as Peking cabbage, Chinese leaves are long slender leaves, pale green in colour. They have a very subtle cabbage flavour and a really crisp texture. Chinese leaves have the ability to absorb other flavours and are often combined with rich or strong-tasting foods."

I think ARUGULA would be a good substitute -- it's got the peppery lettuce thing going on (and I am always trying to get out of eating cabbage anyhow). ;)

Hmm...I wonder if that might mean that I SHOULD have cabbage???