source:
www.radioshackcatalogs.com (1989)
Those look to be
extremely generic tweeters.
In a perfect world, you want to match the impedance, sensitivity (dB of sound pressure level at a fixed measurement distance per a fixed level of power input), and resonant frequency (Fs) of the original.
In this case, a pair of these is probably fine.
https://www.parts-express.com/goldwood-gt-25-3-cone-tweeter--270-018
or these...
https://www.parts-express.com/t-25-2-1-2-paper-cone-tweeter-8-ohm--279-452
Worth checking MCM Electronics, too -- the site is down as I type this, however.
EDIT: It's worth mentioning that the OP should
probably ensure that, for each of the malfunctioning loudspeakers, that the problem
really does lie in the tweeter and not "upstream" in the loudspeaker (i.e., in the crossovers). The simplest way to do this is probably to swap the two tweeters and see whether the "distorted tweeter" works the same in either cabinet
and the "nonfunctional tweeter" also behaves the same in either cabinet. If not, the problem(s) is/are in the wiring or crossover networks, and not the tweeter(s). The most likely culprits in the crossovers would typically be capacitors. If that particular loudspeaker has any "protection elements" (e.g., a "Raychem" self-resetting fuse, or a light bulb in series, or a fuse) in the crossover to protect the MR and/or tweeter, those are also potentially suspect. Resistors and inductors are less likely suspects (but
never say never, you know?).
The other good way to check the health of a suspected "nonfunctional" tweeter is with a DMM (digital multimeter), if available. Set the DMM to measure ohms, remove the tweeter from the speaker (disconnect the wires) and check the voice coil's DC resistance (one meter probe connected to each of the two terminals on the tweeter. If the voice coil is OK, the DMM will read a value of a few ohms. If it reads "open" (infinite resistance), the voice coil is open. If the reading is
very low (close to zero ohms), the voice coil may be shorted.
Another way to check a driver is with a battery (e.g., a 1.5 volt AA cell). Remove the tweeter from the speaker (again, disconnect the wires). Connect two tweeters to the two terminals. Hold one cliplead's other end to one terminal of the cell. Touch the free end of the other cliplead to the
other terminal of the cell. If the tweeter is OK, you'll hear a "click" or a quick rustle of static. If you hear nothing, the tweeter probably has an open voice coil.
Worth mentioning that, especially for a tweeter,
don't leave the voice coil 'energized' with DC (even at 1.5 V) for any duration of time. It's not
likely to overheat and fry the voice coil -- but it
might.