IIRC Sunbeam produced the C-50's well into the late 1960's or early 1970's so yes, there should be a decent supply lying about spare.
One reason many C-50's either are MIB or were used only once or twice, then put away and forgotten, is the fact that it does take some "tweaking" on technique to get a good brew. Units heat up very hot and are so heavy that it does take forever for the lower pot to cool enough to draw down the coffee from the upper chamber. So long in fact one can end up with burnt tasting and or over brewed coffee.
Still, am not willing to pay $150 or so for a vintage unit, so guess I'll be joining you and sussing out flea markets/ estate sales or that eBay gem.