The most common one that is reasonably good is Gold Plum (Zhenjiang, or Chinkiang vinegar) in the yellow bottle. I believe its a 2yr aged black vinegar and they also offer a 3yr. Its the classic version made with rice and some wheat bran. Shuita (Shanxi vinegar) is not made from rice and its more uncommon outside China. A little more expensive too being aged 5yrs. There is also Sichuan vinegar called Baoning. Most commonly used in food from Chengdu and surrounding areas. Its wheat based.Still have no found black vinegar either. But then all I really need to do is go into Dallas 30 minutes or so away and I can find it all I'm sure.
IMO avoid nearly all black vinegar from Taiwan. I havent tried one yet with the same authentic taste. They add colorings and other stuff to all the ones ive seen.
Gold Plum and Hengshun black rice vinegar will more than likely be the most common in a good market. Better markets might even have some older Hengshun. They do offer a 6yr aged. Its rather pricey on Amazon.