I totally agree that not being able to get the parts sucks, but it’s worth pointing out that most of System76’s laptops are barebones models from Clevo, whereas Purism designs its own laptops, which means it has very small production runs and can’t get replacement parts very easily.
Ideally Purism would order extra parts when it makes another batch of laptops, but this costs extra and Purism will likely lose money stocking parts that it may never be able to sell. I looked at this same issue, and decided to buy a Thinkpad instead of a Librem 13, because I know that I can get Thinkpad parts on eBay.
Another solution is to have a 3rd party company that collects used Librem 13/15 which are broken for scavenging parts in order to set them on eBay.