Are you sure the cabinet isn’t a SMLD? Those look like SMLD/S-avp speakers. I can’t quite tell from the picture what the cabinet is.
Either way I have seen people just use regular computer speakers. It’s tougher with a SMLD because there isn’t really space inside the cabinet. A G23 has enough space to fit small computer speakers in place of the original speakers.
If you can’t find direct replacements You should be able to use any similar size speaker as long as the impedance is the same and they are similar wattage. Someone more knowledgeable than me may know the specs on the speakers.