Controlled vertical dispersion? Really? More like "Out of control" vertical dispersion. The first Corian D'Appolito loudspeaker I ever designed and built was from that book. I also have Dunlavy SC-1's in storage. I bought those in 1996.
Used several of these for over a decade. Loved them, but got tired of them breaking. Switched over to Minidsp 2x4HD's but still have a Behringer DCX running the subs. When it breaks, that will be it for the DCX's
Based on nozzle size, these should fit too. Getting them today. Great value if they work.
https://www.amazon.com/Earphone-FEYCH-Replacement-4-5-6-3mm-Earphones/dp/B07SN4HP5Z