An Airbourne air motion tweeter (heil like) from Meniscus About $40 ea. or the other for $98 ea.
All this depends on what your using for a full range, and your amplification. Spl of the FR you want to match. I believe this heil tweeter is 89 Spl but, will probably sound great.. If your using tube amplification, and a high efficiency FR in the Jericho horn, then I would go with a top mounted Fostex will be nice as it sits on rails....But price is about $180 for each! Ouch! but will be the best in terms of a super tweeter you can get for the Price range! Madisound sells these Fostex and they look like an aluminum cylinder, Hope this helps Blonde-pianist