The following notion might be distressing to some members, reader
discretion is advised:
If all else fails you can just use standard knobs in many cases.
I replaced the upper three knobs on an AM502 with different black ones
and it doesn't look all that bad.
You can even make stacked knobs by drilling through the larger one.
By replacing all three that were a similar design it isn't as obvious
that they are not original.
I can provide a photo, for your amusement.