Just offering a possible explanation concerning the unavailability of a replacement amp and the need for factory repair -- a product like this probably uses an off-the-shelf power amp module. Combine that with the current trend in manufacturing for "just in time" raw materials and parts -- a production facility works with their suppliers to have parts delivered as-needed rather than having single big shipments of parts with the manufacturer having to store them as they draw down from their own warehouse supply.
Now, say that the amp supplier discontinues that model and brings out a new one. That's not an uncommon issue for manufacturers using a standard part from another supplier. The new amp may be electrically as good, or better, than the discontinued model. However, it may no longer be an easy physical fit for the speaker. As such, switching out the old amp for the new one may no longer be a simple swap that a customer could do.
Just a thought...