We just received new stock of the Transducer lab tweeters with the old style, rectangular face plates.
Most are the "X" versions - epoxy adhesives. http://meniscusaudio.com/transducer-lab-m-88.html
These tend to sell out fast, so you might want to consider them. Still no word on the new, round versions.
There is an odd number of two of the models, so you could also do a center channel.