Did you try the old suck-the-domes-back-out-with-the-vacuum-cleaner-
trick? I don't know if it will work on a metal dome, but it's worth a
shot since they're broken anyway.
You're going to severely limit your options if you insist on staying
with the same footprint. A little careful work with a good sharp
chisel might turn the trick.
There was a salient comment made about modifying the crossover to work
with the new driver. If the inductance, DC resistance, efficiency,
and frequency response of the new part are close, chances are you'll
be OK there. Those would be better selection criteria. Unless you
have access to the tools and design skills, it would be better to
modify the mechanical mounting,
I recently replaced my aging Philips ribbons with a pair of Morel
CAT308s,
http://www.madisound.com/catalog/PDF/CAT308.pdf. They're a
bit pricey at $75 a pop, but well worth the money IMHO. Flat, clean,
efficient, and they'll handle a lot of power.