Lack of spare parts, especially OEM parts, for manufactured goods is
pretty much a direct consequence of just-in-time manufacturing
throughout the supply chain.  The less expensive the item means the
non-availability of parts is only offset by the fact that some parts are
commonly used in both multiple models and some parts are standardised
(though of course again this level of commonality or standardization is
least likely for cosmetic parts).  Often at best you _can_ likely get
non-standard parts during the period that an item is covered under a
full warranty, but even then you might only get a complete replacement
item (which may differ slightly, especially in cosmetic aspects).  One
exception to even standardized parts are critical functional OEM parts
auto parts which are forbidden for "older" automobiles in the EU.  This
is done in an attempt to get older polluting or unsafe vehicles off the
road.

In the world of appliances a good independent repair technician can
probably source "compatible" parts, even for cosmetic parts, due in no
small way to the number of times people will choose not to repair an
item, thus allowing its parts to be salvaged by anyone with the time,
interest, and storage capacity.

Where OEM parts are available one often pays severely for their storage
and distribution.  I have an antique motorcycle made by Honda.  I can
still walk into any Honda dealership today and find the parts diagrams
and lists on the computer there, and there are a good number of parts I
can still order from them, if I'm willing to pay this premium for the
OEM part.  The premium is high.  I made the mistake of ordering a very
standard 6mmx20mm bolt for about 100 times the price it would have cost
had I got it from anywhere else, but it came in a little plastic bag
labeled with the Honda logo and the Honda part number specific to my
antique bike model and year, and for all I know it was likely air-mailed
from Japan.  BTW, the bike is a 1984 V45 Magna -- still very
serviceable, but tending towards requiring third-party parts now, and
firmly in the antique category under BC law.