^^ maybe I'll call them tomorrow. I'm guessing they don't have parts for speakers from 2 decades ago, but i guess it's worth a try.
Rui, I'm not familiar with the AX120. You show pictures of the front, but not the back. Is there not a low level input that can be fed by the receiver sub out so that the high level inputs on the front aren't needed? In any case, to see if the sub amp even works now, connect just the right channel input spring clips, which appear to be okay.
No, this sub only has these speaker inputs.
I would guess that spring clip panels are available at Partsexpress
here. (Check page two of the results also)
Edit: Maybe
this one in particular?
If you can't find one the exact size, you could always "plug" the existing terminal plate space with a block of wood and mount the new plate over a larger block of wood.
It looks like you've already unscrewed the terminal plate to check it out....
Thanks Mark. Your specific link seems to be a nearly identical part. I hope shipping doesn't jack up the price.