Any parts store should have them. I can't believe they don't. You can also go to a trailer shop and they should have something that will work. It's just a common dust cover???
Dust covers generally aren't by model specific application unless you are at a dealer. They go by diameter( 2", 2 1/8", 2 1/4", etc... ).
This should not be something hard to find.
GO to an actual store and try asking for bearing dust caps or wheel hub dust caps. They may not have it by application so you may need to pull a rotor and then find one that fits. Look for the old cranky guy as he is most likely a long time parts guy who actually will know how to find a part when you can't punch it into the computer. Chances are the pimpley faced punk won't know how.