Watch eBay. The Vifa/Tymphany D25AG-05-06 was used in quite a few different makes and models back in the '90s. So, used, but working examples show up with some regularity. Just be sure you get the D25AG-05-06 and not the D25AG-35-06. The latter won't work as a drop in replacement. If you're on a time crunch or want to try something newer and improved, the folks at Madisound offer a service to this end and can probably do a decent job parameter matching one of the offerings they have in stock. Just plan on spending $2-300 for a pair of whatever they recommend.
What probably happened with that one is the ferrofluid went dry and without its cooling properties the voice coil cooked almost to popping open, but not quite. I suspect if you were to measure it and the working tweeter, you'll find this one has a much higher DCR because of that. Ferrofluid in drivers designed for it is there for a reason. It serves several important functions, cooling being just one of them. The other is damping, which is a desirable quality in a driver, and is absolutely needed with metal domes like these to keep them from ringing. Some mistake the ringing for louder and louder for better, but it's really just an ice pick to the ear source of distortion. The Fs also changes, which usually will impact the behavior around the crossover point. The removal of ferrofluid is some whacky tweak from the '80s developed by those with no clue how drivers work. Things like this is why I shy away from buying old speakers from enthusiasts. Usually have to put more effort and money into undoing their hoaky hacks, "fixes" and "upgrades" than I would with something less 'blessed' by the handiwork of Saints Dunning and Kruger and simply left alone.
