I have seen an advertisement locally for a computer (no longer in production ) for sale, with the warning that buyers must appreciate the model is now extinct , therefore can not be maintained easily.
I don't think the model is ' extinct ' but I can't for the life of me remember the word I may have used .
Something that has been superseded is known as what ? ...
Obsolete certainly fits the description you have given; something which is no longer made as it has been superseded by something better (e.g. VCR/DVD) and parts are not therefore easily available.