I have reported Goldwood Piezo Tweeter before in my earlier articles. It is a cheap and good tweeter according to the review in the link below. The price is slightly increase by still around USD2/piece.
Last week my brother went to US for business trip. I only asked him to buy 10 each tweeters for me to try out. The parts now with me. I will do some testing and compare with my current tweeters. I will post the results once I have tested it.