Likely no surprise to most if not all, Sphere in Canada has the AA 501A parts I need, with some caveats: the knob is a dark grey type rather than light grey as originally fitted (no big deal there), and the side panel is missing the 1/4 turn latches. I have a separate thread I started about tips for removing or repairing those, or if there are possibly replacements available.
Anyway, just wanted to follow up.
Thanks again for all the helpful info!
Cory Oace